Compared to AH the .50s in FB are crap, no D800 smack downs. However, if you get in close and fire at convergence they do all right over there. They shred Japanese planes well enough. Last night I flew a few Pacific coops in the F6F and the Jap planes fell a part with short aimed bursts. The Hogs aren't as easy mode as AH but fun enough...
I fly mostly LW aircraft and its easy enough to avoid the instant death from most Ami planes (.50 cals). As long as you don't sit still they may ping you but nothing major will fall off.
Hispanos, aka Hizookas, shred over there just like in AH. If a Spit or Tempest or Hurri IIC gets saddled up on your 6 you might as well just bale. SvHaks are far more deadly there then in AH. So is the MGFF/M and Type 99 MK I and IIs.
3cm there is a little less lethal. Some times planes like a spit can take 3 or 4 3cm hits before falling apart. Just tonight on the Warclouds server my wingman drug a temp and a Spit up vertical and from 50m I landed 2 3cm hits on the cowling of a Spit and he flew home and landed. Heavily damaged but able to fly. I had to deal with the Temp and couldn't finish him.
MG151/2cm is about the same just the hit sprites are prettier in FB. The smaller caliber mgs (.303s, 7.6mm etc...) are in general more lethal in FB then AH.
All this may just be due to the different approaches to the respective damage models. FB is basically a box game with an online component and as such it can't compete with AH in terms of a 'just logging on for a quick furball' but it has other attributes that make up for it. It all depends on what you are looking for. There's a greater variety of planes and most of the better servers cap out at about 32-50. There's a few 64 and 100 player servers as well.
Unless you have FB/AEP/PF (the original Il-2 is long dead) patched up to 4.04m or 4.05m (Pe-2 add-on) you won't find any servers.
Hyperlobby is what a good portion of those who fly FB online hang out but you can use, ASE, gamespy etc...