If your 5'10, get 191's for sure.
I'm only 5 ft and I'm on 185 ep's.
i am almost 6 feet tall and i am getting 181 reno rockers.
with really rockerd skis onl a small surface area stays on the snow when it is flat. so its a matter of how much extra length on the ski you want. any size is good for you. Personal prefence.