I like my 6.5 square . With it i am able to cut smaller squares or pieces at my sit-down ironing center rather stand at the cutting table for everything. I also like my 5" sq. and 2.5 sq. but acquired them (as with each ruler) when I needed it.
being able to read them is super important . I cant have too much jazz on my mine. I like clear ones with thin lines the best.