IMO 3" strops are lame and cause you to strop improper if using a traditional barber strop(which are a perfect 2.5"). The stroke you are learning on your starter carries over to a professional barber strop whereas you will learn from scratch on a 3" with straight strokes.

I prefer vintage shell strops in barber style, 2.5" wide with no handles or D ring. Call me old school but it works perfect for me, so why change it.