Around Y2K I was in a fabric swapping group before the 10" square was a precut size. We started with a bug fabric swap and decided on the size for a number of reasons -- one of which it was a pretty easy way of cutting fabric. But also because it gave you enough room to work around getting a full design from large prints.
LOL I am STILL using some of the squares and themes. They stored very well for me in boxes I got from work that held packets of coffee. It is easy to find a 12x12" box. They are easy to cut down for scrap or themed quilts.
I tried the 2.5"strip but it always seemed I needed 2" or 3" strips instead, or that I would spend the rest of my life doing nothing but patterns that required 2.5" cuts -- and there are a lot of them! A lot of people like that idea but it sort of scared me.
Using my mantra of "I can cut down but I can't cut up" I have decided to only save 6.5" strips larger than a square. Anything less than that I give away and I am trying to use up my remaining 10" squares
Hope you find what works for you!