Clank doesn't have more health than anyone. There are essentially no differences. Quark and Clank (after he transforms) are a bit bigger and bulkier than Ratchet but their movement and speed are the same. Ratchet just feels faster because he's smaller.

Qwark and Clank are more annoying to listen to due to Qwark's somewhat grating voice and Clank's constant giggling (it was funny the few times it happened in the first few R&C games, but constantly throughout this game, no thanks).