which pokemon is better

[PkMn Trainer Black]

My personal opinion: Slaking + Giga Impact+ Choice Band = Win

true, but if someone comes in with a good STAB fighting move; maybe even focus blast with a special sweeper on a rest turn and a choice scarf, that Slaking is going to have some trouble, Snorlax has a much higher survival rate at that point and time

You wouldn't even need that. Giga Impact forces Slaking to rest on the Truant turn. This means he can no longer switch out during his Truant turn.

The way Slaking rests, you could win with one move: Protect. Simply Protect on the turn that he is not loafing around and you are guaranteed to take no damage from any of his attacks and are now free to use the Truant turn as an attacking turn.

That, or you could use fly to kill him off (slacking, of course)

[Chad29]

fly or dive are both good. There are various ways to kill Slaking, as with most pokemon, but that is if you have something prepared for one. If you don't have a pokemon with fly/dive, protect/detect, or something like that you are in trouble. As I think I said before, not many pokemon can take a hit from Slaking, and unlike Snorlax he doesn't need setup time to be a devastating threat.

They're both good for different reasons. Slaking can kill almost anything in one hit if he gets the opportunity, and Snorlax is an excellent sponge if he can set up with curse or gets baton passed something good.

[Frenchfry]

It takes an aweful lot of preperation/overlevelling to OHKO anything, even if you're a slaking. Besides, Protect/Detect/Fly/Dive/Bounce are all fairly common.
And unless he DOES KO in one hit, you might as well halve all his stats, because that's pretty much what the one-turn delay is doing by making him only be able to defend himself every other turn.

[DarK_SouL]

I voted Snorlax, because mainly Slaking can only attack every other turn as someone else said.

Partialy because of my Snorlax's awesome moves:
SolarBeam
IceBeam
Flamethrower
Earthquake

Plus Slaking doesn't learn any good moves in my opinion.