So from what I can tell if you use the grenade launcher, it'll replace the frag grenade in your arsenal, but my question is how does it perform differently from the dinky normal grenade?

I mean attaching the grenade launcher to your gun deducts stats from almost all of the stats on your gun, so it should give some advantage imo.

Also does grenade spread skills for the Soldier class affect the grenade launcher attachment?

The attachment is used when you would throw a nade. it goes further and detonates on impact.
Not sure about the lobster, but the Auto-Nade also detonates on impact

Thanks. That might actually make the grenade useful. .

I have read that some grenades launchers will have a short fuse that starts after impact. This is to make things more tactical, like bounce it in front of target so it explodes by time it gets to them. I would also imagine that launchers will have a shorter cooldown to fire more quickly. Also, remember a single grenade will not kill. If a player has 1 HP and takes a grenade, they become incapacitated with the full amount of that states HP. The damage does not blast through. This is similar to how the sheilds work in Halo : Reach.

Lobster grenades bounce once, then detonate like 1 second later.

Soldier's frag grenade AoE boost doesn't affect the launcher. The frag grenade damage boost, on the other hand, might. I say "might" because it doesn't actually say one way or the other, so I assume it does, but I'm not 100% sure.

It doesn't have to kill.

All it has to do is knockdown.

The normal grenade does that, but from all the other vids I've seen, due to its long detonation time and small splash damage radius, you have to be brain dead to not avoid it.

Underslung nade launchers are impact, EZ-nade launcher is impact, Lobster is on a timer

These grenade launchers won't be as bad as NOOB tubes I hope. Right?

That's exactly what I was thinking.

grenades won't kill unless you are already hurt. they will knock you on your ass or face, allowing someone to come up and crush your face with thier gun butt, or slash your throat with a knife. so avoid grenades whenever possible. brought to by the EZ-Nade, the Heavy answer to bouncing Lights!

They won't be. The underslung grenade launcher deals the same damage as your regular frag grenades, i.e. not that much. It's mostly used for crowd control and for knocking people down. Plus, it can only be used once every 30 seconds (20 seconds if you're a Soldier with a certain ability). Still dangerous, of course, but you won't have to worry about getting insta-killed by 'em.