Hi brok,
I am by no means an "expert" but I am 5'2 and ride a 47cm Trek 1500 WSD. Ah the Madone....*wiping up drool*...
I think if your bike is below 50cm you shouldn't be too concerned because it should handle just like a 700C wheel on a bigger bike. How tall are you? If you are petite like me, riding on a 650C would be more suitable.
I also don't think some bikes in smaller sizes can even accomodate the bigger wheels. Also, because it's a bigger wheel I would imagine the 750C moves over the road better but the 650C are more aero. I know lots of triathletes who are not petite that ride on 650C but they do so on a tri bike and not a road bike.
All limits are self imposed - Icarus