I guess tavern one is better when fully moded( for pvm)
swp is slightly better for pvp ( but still he attacks only one enemy) + his mods dont work
usually he attacks enemy support since thay have the least hp( genrally speaking/ not always true) so if built well he may kill or do great damage to the support who has the least hp
u can always find better assulters in tavern as lvl progresses
Shin zabimaru by far, his skill is much stronger pvp, and he does good damage for pve.
He has good grow rate and later you can upgrade him, then he's very good pve, and pvp with a superb skill.
renji abarai is just a good damage dealer, but little use in pvp and really not good late game.