I use my 6 x 24 the most and my 6.5" square second most for squaring up HST's and other small patches and for fussy cutting.
I don't fold twice if I can avoid it because I also suffer from the V strip problem no matter what I do. Even when I use my Alto Quilt Cut--I have the V problem--RRRRRR! I use the Alto for cutting scraps into useful size patches.