I always advise getting the full ammo load. Why leave 400 lbs on the ground when you can simply throw them at the first enemy that crosses your path? Go crazy with the guns till your counters reach 1000 each, then you have the low ammo load. Unlike some other planes that get a ton of useless 0.3 ammo together with the main guns, in the jug the entire load is useful.
True. You can't go "wrong" with a full load, just my recommendation for A-A work. I was approaching it from the standpoint of getting a little more initial climb, a little more slippery from the get-go if defensive and still having 5-9 kills available. I started landing with ammo in left over and liked getting away from the "spray and pray" mindset. If I can get 5 kills without basically carrying a 500lb bomb around, I dump the weight.
Here's a aircraft comparison that might be useful:
http://bbs.hitechcreations.com/smf/index.php/topic,264759.0.html It does appear "best sustained turn" goes to the N. (At least before the M)
Did a quick test on this.
A P-47D-40, 50% fuel, has a sustained WEP climb rate @5K of 3288 fpm with the 8 guns, full ammo package. With the 267 rpg option, it's 3429 fpm. That's 141 fpm more (4.2%)
Did a test with my D25...
D25 (8x425) w 75% fuel, 14,370lbs=2390fpm@2.5k
D25 (8x267) w 75% fuel, 13,670lbs=2500fpm@2.5k
D25 (8x425) w 50% fuel 13,810lbs=2545fpm@2.5k
D25 (8x425) w 50% fuel WEP=3093fpm@2.5k
D25 (8x267) w 50% fuel 13,420lbs=2663fpm@2.5k
D25 (8x267) w 50% fuel WEP=3226fpm@2.5k
"Couple hundred" is an overstatement after all...(but I still take the light ammo package darnit!)