All a question of personal preference really, and body shape.
I'm 6'2 and can ride either an 18" or 19" Kona. I slightly prefer the 19" but with a long seatpost and longer stem the 18" is fine too...
I have monkey arms so don't find any issue with running long stems, other people may not like that style but as i say it's so personal there is no hard and fast rule by height..
Doesn't really help much does it..