[ruiny]

I had a 150 and hated it, (same footprint) but loved my 180.

If the 6 feet long of the 125 is ok and the 2 feet wide of the 120 is ok than a 180 is double ok.
It will cost a bit more to set up. But if stocked the same as the smaller tanks not much more. And it will be alot nice than either.
I have had a 75, 180, 280, 150, 93cube in that order.
My favorite was the 180 by far.

But if you must choose than the 120 gets my vote.