First, I'd like to flex the fact that I got Kyo and Gowther after 2 draws
Red Gowther just covers more ground. Green Gowther's ULT depletion makes him the best character for managing your enemies ULT gauge. Seriously, I did a few PVP rounds with him, and the entire enemy team had like 2 Orbs at most when they died. If you have a character with attack disables, or just find ULT depletion better, then Green Gowther is better for your team, but Red Gowther is more flexible.
10 Anvils a day is also a plus for Green
Edit: Halloween Gowther's Unique is useless for certain teams