I just personally couldn't justify having two iPads, but from the brief time I owned a mini alongside my Pro I can say that it had an AMAZING form factor for handled games. If I gamed more on iOS, I'd seriously consider picking up one of them.Just make sure to use a game controller. The only iPad I've used that felt comfortable with onscreen controls was the iPad mini.
I mean at 6GB the 12 Pro has more ram than any iPad but the Pro. It would probably perform better than the iPad Air which has the same a14 but only 4GB. Otherwise I agree.If you want to do a lot of gaming on iOS, the iPad is probably better suited as it has the larger screen, larger battery and a lot of times more RAM.