Danny Ocean said:
The magnum only has an 8-round clip, is slow to fire, and is a tad more inaccurate. It's not really worth it... until you consider its stopping power. Seriously, this thing can decimate whole hoards! The bullets just keep going! Plus, you can use it when you go down, unlike a melee weapon.
Wash your mouth out boy!

The regular pistol has a 15 shots per clip, and on Normal difficulty you need 2 non-headshots to put a CI down, compared to a 1 hit kill 90% of the time with a Magnum. As you say though (probably because we've had this same conversation in game...) having a weapon that can tear limbs off when you're incapped is extremely valuable, especially when you're providing "ground cover" (shooting a SI off a team-mate whilst you are incapped).
I personally prefer the magnum for one simple reason: It gives you a visual queue as soon as it hits. With a pistol, you have to watch for bullet wounds in the target, or the target falling over. If I fire a few hurried shots at 3 CI and see 2 legs flying through the air, chances are I need to make sure the third one isn't still upright.
As for the AK47, it's perfect for people who doubletap (like myself). The clip size is big enough to allow doubletapping of large groups between reload, and the quick re-focusing means you can hit headshots reliably with it. You sacrifice the spread and stopping power of a shotgun, but I've not had any problems with ammo conservation like I did with the assault rifle/smg.
Tactics wise... Remember the difference between Boomer Bile and Pipe Bombs. Pipes attract any zeds ALREADY IN THE AREA, then blow them up. Bile spawns a hoard and attracts it to the place you've thrown it. If you're running towards a safe room on b+w 5hp, throwing a pipebomb into those 20 zeds ahead is an infinitely better idea than throwing bile, as once it's died down the 20 zeds have become 35.
Mics are useful, make sure to call as much as you can. If you think you hear a hunter, say "Hunter on the Left I think". Someone will confirm or deny it, but if no-one calls it and the one person who's not paying attention gets pounced, you'll regret it. Likewise, if you walk into a room and see a healthkit/pills, take a second to look at the bar at the bottom. If someone is without a kit or low on health, call it. If not, ask if anyone needs it before taking it. Weapons are like this too, someone may be low on ammo. Standing next to the item and flashing your torch on it helps immensely when someone says "you said there's X here, where is it?"
On scavenger events like those at the end of the first campaign, we found it was better to send two to collect, then throw the cannisters down to the other pair who were fueling the car up. It saves people running up and down stairs.
I've got in the habit of doing 360 spins once in a while. It helps to know exactly where your team are, who's limping, who's got the grenade launcher and so on. This leads onto my next point actually, Pairs. Two pairs doesn't work as well as one quad, but it works a lot better than four individuals. If you see someone is lagging behind, fall back and buddy up with them until they catch up with the group. Likewise if you see someone starting to break away from the group, make sure someone stays with them. It won't help a second-perfect double-incap, but even managing to melee the hunter off the other person before you get smokered is worth it.
That's all for the time being, but I'm sure more will come up... All this talk of it makes me want to play... Danny, you up for a game?