The ergo design of these will change your ride for ever! Riding with simple round grips are not near as comfortable once you make the switch. When you think about it, we are making three points of contact with the bike (Seat/pedals/grips), yet the advancement in grip design has been very slow in coming.
I use the small size and I am 5'7". I had a pair of the large at one time, but found them a little to big for my grip, which meant sore hands, so choose the size wisely! I've had the Ergon GA1's as well and seem to like these a bit better.