good to who? the best like levrone , flex , dorian etc are all 5'9 plus..the reason you think they are the best is because there are so many of the lil fuckas..
The best BB are all 5'9 plus this is fact.
Yes, the guys 5'9, 5'10ish are probably the best height for building if you consider structure, symmetry, aesthetics with mass. Shorter guys look too compact although pound for pound many of them out-muscle the taller guys. If you look at the Mr. O history, almost all of them are about 5'9-5'10 with the exception of Dex, Zane etc.