I don't think Mauer will ever show power. He was hot in the first half last season but hasn't shown much before or after in that category. I also think Brian will hit 30 home runs a few years. If he was hitting in a hitter friendly field he might already be there.
Mauer is a beast with average, but that might even take a hit playing outside in cold weather for his career. I just wish Brian had that DH day.
I think they are 1A and 1B, with Mauer having the upperhand now. But Mauer is a year older and you have to take that into play also.