There's a couple of really good comparison videos that have been done, but this article summarizes the differences and shows a bunch of different videos of different versions of the game.
If you're looking for a quick heads-up comparison of the video quality, check out this YouTube video:
Grenade launchers ('noob toobs'), sniper rifles, C4, and other explosives are all pretty useful, but what you need the most is time.
If you can find a place where you can see them at a range, or you can glitch them into staying away from you, you'll survive a lot longer. I've killed quite a few juggernauts in co-op with a friend, and usually I'd be the 'bait' while he laid down somewhere out of the way with a sniper rifle and laid into them. When I could I'd find a place to hide and shoot them with explosive weapons, or, in a pinch, an LMG.
There are some areas where you can let your friend 'die' and they will keep the juggernauts busy while you kill them. The most popular is to block a doorway with your co-op buddy's downed body. You have to revive the buddy every so often so that you don't lose the match, however.
In Modern Warfare 2, I also found that juggernauts would freeze if they were unable to path to me - hiding under a table helped, for instance. They'd just stand there, unable to determine how to get to me, and I'd snipe them in the head over and over again.
If co-op "cheesing" them isn't an option, and/or you've got cash to burn, there are a few weapons and special items that can help:
- Sentry guns can do good damage to Juggernauts, although they will destroy them quickly if left undefended. They also take a good long time to get spun up, and won't even try to lock onto a target if you're standing in an area anywhere between the gun and the target. On a Juggernaut round, I'll tend to move my gun to a position where it has a long line of sight on the enemy, and I'm standing closer to him than the gun is.
- Predator missiles and air strikes can quickly kill a single Juggernaut, or perhaps a couple if they're bunched together.
- Riot shield teams are moderately effective against Juggernauts. You may lose a couple, but if all four are focusing fire, they can take down one on their own most of the time. If you're supporting them, (or a sentry is) you can often get away with fewer losses.
- Items that increase your survivability (auto revive/body armor) are obviously helpful.
Flash grenades are the surprise winners here - they can stun a Juggernaut (and in the riot shielder's case, cause him to drop his defenses) so that you can go for headshots without taking damage. Also, since the Juggernaut(s) aren't firing, the effectiveness of your other items is also increased. The only downside is that their head tends to move while they're stunned, making headshots harder.
Best Answer
When I play survival, I tend to "live off the land" and take weapons off of dead enemy soldiers instead of buying weapons at the shop. In Resistance in particular, it's pretty easy to set up shop in the center house, like I explained here:
What is best sniper position on Resistance in Spec Ops: Survival mode?
Remember that you can also carry two primary weapons in Survival - so if enemies are using AK-47's and ammo for that is plentiful on the ground, you can use that gun alongside another AR that you've purchased or found in an earlier round. Between rounds you can go back and just buy ammo, or pick up upgrades for these weapons if you prefer them.
Having 2 ARs means that if you empty a clip and there's still a lot of guys to shoot, you can switch to your off-hand AR and continue firing faster than you could've reloaded.
I don't tend to like LMGs or SMGs, the LMGs take too long to reload, and the SMGs do pitiful damage against enemies in the later rounds. You might find them useful, depending on your strategy and preferences, however.
Not buying weapons means that you have more cash left over for other things, such as sentry guns, squads of AI helpers, and air support to deal with Juggernauts and other difficult situations.
Here is the weapon list and their rankings:
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