Who should I rank up?

Sllayer05

I want to know who would be better to rank up a 5* Medusa to rank 4 or a 5* Venom to rank 3 and neither of them are duped.

Fingfangfoomfanes

Venom is more fun to play with with all his mutation buffs. But Medusa hits like a truck and leaps and bounds in PI when duped.

Venom for me.