I raise queens, but even if I just want to bank a queen to make a good hive queenless for a cell builder or whatever, I use my medium depth two frame mating nucs to bank the queens. But a real queen bank, to me, means you have several queens in a nuc still in their cages. I prefer to have then in the two frame nucs, though because they can lay and are ready to go when you want to put them in a real hive.
I have nucs of many sizes:
http://incolor.inetnebr.com/bush/images/AssortedWidths.JPG