10 is better than 12.
For now, I might agree with you. I like both 10 and 12.
Once we find out what the new post season format is going to be, I may change my tune. Right now, EVERY other conference that will be in contention for the national title besides the Big 12 (SEC, big 10, PAC, ACC) has a title game. If the playoff values SOS as highly as is rumored, those conference championship games will provide a very valuable SOS bump for those conferences, an advantage that the Big 12 doesn't have.
Suppose there is an undefeated SEC team (LSU 13-0, defeated Florida in title game), and undefeated PAC team (USC 13-0, defeated Oregon in title game), and 1-loss teams from the big 10 (tOSU 12-1, defeated 10-3 Mich in title game), ACC (FSU 12-1, defeated 10-3 Va Tech in title game), Big 12 (OU 11-1), and SEC (Florida 12-1, was undefeated until they lost to LSU in SEC title game). Who gets in?
Obviously, LSU and USC would be in. But there are four highly ranked teams in contention for the remaining two spots. Will OU be harmed by playing one fewer game than the other contenders? Especially since that extra game all those other teams have was likely against a very good opponent?
There are lots of questions that must be answered before we can really say which size is better. I'm still not sure that FSU is actually going to leave the ACC, but if they do leave the ACC, I strongly believe it will be AFTER the post-season format is determined and everyone has a chance to analyze it and understand it as completely as possible.