My *ahem* 2 cents:
Weaknesses: The Spit 16 does have two basic weaknesses IMO though the latter is really a matter of skill. Primary weakness: Toughness. Even though a zeke catches fire easier, when I'm low on ammo I target Spits. Those dainty wings are all too happy to pop off- and oh it is beautiful. Secondary weakness: Short clip. While many pilots can get several kills with Spits the clip IS a little on the scanty side. The desire to line up a "good" shot only lengthens the amount of time exposed to other enemies in the area. Combined with its lack of toughness a Spit is especially vulnerable when "sealing the deal."
Opinion: The 16 is indeed "easy mode" in terms of maneuverability- it is an amazing point and click machine that has a major edge over virtually every aircraft in the game (speed, turn, climb, roll). It seems to do everything very well short of running down the speed demons. The problem with all Spits is that you are always one ping away from dead meaning you can't sacrifice even the smallest snapshot without seeing your cartoon pilot life flash before your eyes...and as we all know, in the MA 
happens. So while the 16 may be "easy mode" in terms of getting shots, it is "insane mode" when it comes to surviving them and requires a superior level of SA to actually land kills. It does seem that despite their wide use, 16s land proportionally fewer kills then other LW rides. You can create shots with virtually any fighter in the game but after pilot SA, aircraft survivability is what makes or breaks a k/d ratio. (And yes, in general it seems the average 16 driver is below par.)
Relative to the 14: The 14 may be better in terms of climb and speed but the 16 has big advantages in the areas of stability, turn and roll. Since I consider speed the single most important factor for fighters (allowing engagement at the time/place of your choosing) it is hard for me to argue against placing a lower perk value on the 14 relative to the 16 even if it is an inferior furballer. Both aircraft are beasts with the 14 requiring more time to master. Given the relative parity of these two aircraft in the hands of the average pilot it seems logical to me to either attach a very modest perk cost to the 16. IE 1-2 points perhaps better yet, unperk the 14 and have the MA cope with all the lethal K4 drivers switching to the 14.
Tactics: I like American iron and most of my AH kills have come in the 47,F6F and 38 (in that order). With the exception of speed, the Spit16 generally holds the same turn and climb advantages over the entire US planeset minus the Wildcat and Brew. My best advice for dealing with Spits.
1. In virtually any ride it is a bad omen if you fly UNDER a Spit to engage it 1v1. Chances are you will never hold any initiative in the coming engagement unless you are that rare "uber pilot" or the Spit makes a big mistake.
2. Fly with a friend. A good Spit16 driver will probably beat a good 47 driver in a co-E engagement. You cannot simply run away from a Spit every time you see one Co-E. My theory: (With speed being equal) As the number of aircraft in an engagement increases (and the SA level of the average pilot is exceeded) the premium on turn performance you would see in a 1v1 shifts to the benefits of toughness and firepower. Even though it is natural to expect Spits to be dominant in large furballs, US planes seem to hold their own just fine since they can both take a hit and spray lead for 30 seconds or more.
3. In many vs many go with the jink not the break. If you find a Spit trailing your Jug 600 out and he is not closing, yes you may die. 
.... but consider jinking instead of turning or attempting to force an overshoot. I think this for a few reasons. A. You present the smallest possible target profile. This is a common Spit mistake, they are pulling away in a climb 1.0 out but send some tracers by their cockpit and they perform a break turn exposing the whole of that fragile wing to your mercy. B. Regardless of whether you make him overshoot you just dumped E that you will not get back any time soon. In a many v many this is bad. The Spit has a VERY effective rudder and much less inertia than typical US rides allowing a smart Spit driver to dump E faster when traveling a straight line. Rarely will a Spit blow by you completely, usually a scissors is in order. The problem here is that the Spit turns better slow and has much better roll performance than US rides at typical slow scissor speeds (90-200kts). Against an F6F this is especially pronounced. C. He has a short clip, even if he manages to kill you chances are if you're doing a proper jink (tracing tiny squares with your flight path seems to work well) he has wasted so much ammo as to make him combat ineffective against your remaining buds. D. You're lining his fragile fighter up for an easy shot any green icon should want. Z. In a hypothetical conga line on the deck consisting of say 6 Jugs alternating with 6 spits spaced 600 apart, the Spits should disappear faster than the Jugs. If said line is heading toward friendly territory you've just dragged several fixated Spits to their doom. 
4. 345 is a special number. It is approximately the speed of the Spit 16 on the deck. An aircraft that can sustain this speed can withdraw from a Spit horde so long as it doesn't need to accelerate to get there. FOr US rides this means the ability to DIVE for acceleration. Most US aircraft have superior high-speed handling, if a Spit tries to follow a very fast dive, gaining the upper hand is possible. Early recognition is key. If there are 3 co-alt Spitxteens with your Jug it may be time to evaluate your current skill set and withdraw. The whines on 200 will most definitely not reflect that you may be missing part, are outnumbered, bingo fuel or out of ammo, only that you are a coward without honor. This translates roughly into "Come back so we can have an easy kill." Learn to enjoy it. If you want to furball, turn around, if you feel like living it's your 15 bucks.
5. Last and most disturbing scenario. You are low, Spit16 on your 6 and closing at a controlled rate. In a Hellcat the 6 view sucks, thus it is difficult to accept a faster, more agile aircraft on your 6 and OUT of sight than in the Jug. Altitude permitting (800 ft+ for me) you can induce a spin and hope for the overshoot. The spin move will probably get you nailed at least a little bit but there is the chance that hits will be so distributed around your aircraft that you will not suffer catastrophic damage. In the 51,47,F4U,38 you have a fair chance of actually being able to look back at where the bad guy is pointing his guns. This takes a lot of time but after enough looking down the barrel you will see what a proper gun solution looks like in a tail chase. Depending on range and ballistics (IE a N1K 800-1000 out) you actually have good chances with "See and Avoid", actually dodging bullets after firing. This is obviously not a winning technique if the con is overtaking but for a good overshoot you probably want him within your turn radius. (This depends on speed, faster=bigger) Chop throttle FIRST. The con knows something is up when you roll but slowing due to throttle will delay recognition. Then go about roll, pull, flaps etc. Include rudder inputs for increased speed decay. US aircraft are very stable and with proper rudder a light Jug can virtually hang at 80 knots. Getting a shot after the overshoot is often just as hard as forcing one and your options are fewer now. But! the odds are, at least momentarily, better than when he was on your 6.
6. They are all Spit 16s. MkVIII and up I like a 16. Unless you have a magic method for measuring energy states, treat that IX like a XVI and accept the safety margin. There will always be more Spits later.
7. Don't grab a wolf by the ears. If you can help it, don't slow down for a shot on a Spit, regardless of whether you are in a BnZ ride or not. If you nail him great, but everyone misses and when you do it is guaranteed by Murphy that the 16 driver is good enough to get around on you.
8. Know thy enemy. Flying the Spit16 offline and in the MA a little bit vs maneuvering targets gives a good feel of just how careful you should be with them. They are not great long range deflection shooters nor do they have a big clip. Flying the Spits will define where your best odds are in the flight envelope, just please, don't turn into one of THEM. 
Obviously, Spit killing is near and dear to my heart or I wouldn't have written this book^^^
Kill'em dead! 
All in all, I think that was a very good post.
One thing that I see people use frequently however when talking about how best to fight against a particular plane, (and you use it here as well) is to fly with a friend. That is simply not an acm. It's a tactic, yes, but it doesn't really have anything at all to do with how best to fight a plane.
That would be like in a martial arts discussion about techniques, you say "just shoot him." Yeah, it works, but that's not the discussion.
Not trying to pick on you at all here, you've written a good post, that's just something I see people write frequently that always sticks out to me.
