Malphite:
Ranged single target snare/speed buff (escape)
Melee AOE slow/nuke
Temporary armor buff
AOE nuke disruption ult

Gragas:
Ranged AOE slow/nuke
Dash with AOE snare (escape)
Passive damage reduce 18% (ridiculously good) with HP and mana heal
Huge AOE nuke disruption ult on very short cooldown

Malphite has slightly better defensive stats, but Gragas has Drunken Rage which more than makes up for it (and gives him pretty much infinite sustain). Overall, their utility is similar, but I think Gragas is a better rounded champ who can potentially put out more damage except possibly against heavy AD (where Malph will gain a lot from stacking armor).

What do you think?

Gragas might have a lower Cd ultimate but unless you are communicating with your team Malphite's rofl area knockup keeps being more usefu since the enemy team will probably split and your team will chase different targets in case of a misplaced Gragas' ultil, noneles or notheless(how do you write that word) what you said is what a friend of mine does on the twisted treeline, not sure if it'd work here.

I find him very funky strong and viable when he is free but never to cover the "tank" and initiator role

I think you need to stay outta my bottom lane varus with that gragas. Its annoying.

And he's a fat guy that guzzles alcohol, instead of being a big rock. So he's got that going for him.

Works great, I won the vast majority of my games when I was soft-trolling with tank Gragas top. His ult is a ridiculously good initiation tool, especially because people love to position poorly in Dominion, and his dps is surprisingly high even with full tank items.

I don't think his Q is as effective as Malphite's attackspeed slow, since I'm not sure if it works additively or multiplicatively like Malphite's e does, but from experience I don't cripple autoattackers anywhere near as badly as I do with Malphite.

Problem is Malphite has something gargas doesnt, the -%speed debuff. That is the reason he is better.

Gragas is much less reliable, while still requiring more items and levels to be effective.

All of the usability on Gragas' skills come from leveling them, which is in stark contrast to Malphite.