We got a box of size 2 Pampers Swaddlers as a gift. My daughter has been wearing them. Earlier today I went to change her diaper and grabbed one from the bottom of the diaper bag; it was a size 2 Up & Up.
It was SO BIG on her! The PS fit her snug in her bottom, but have plenty of stretch in the waist. The U&U were much longer AND ALSO stretched all across her waist.
So my unsolicited advice is ... if you are ready to move up a size in the Pampers, try switching to the SAME size in the U&U. (You'll get more diapers per package, which is a lower cost value, and the U&U are cheaper anyway)
Re: PSA: Up & UP diapers are bigger than Pampers