I've only bought precut strips at Quilt Shows. That way, I can actually look at the colors. I should probably carry a small ruler to check out the measurements now that I've read this thread!
I have an Accuquilt Go and cut my own charm squares and strips when I'm using a pattern that calls for them, though that means I'm not getting 1 piece of every fabric in a collection. I trust my own color choices and work from my stash - which will outlive me!