including the 5050 have an internal buffer which will hold several shots. The faster cards will allow you to shoot faster once its full, as they "drain" quicker.
If you're shooting with the internal flash in "auto" mode then it is completely immaterial as the flash will essentially fire at or near full power, and the recharge time dominates. If you are, however, sync'ing to an external flash then its an entirely different matter, as many of them can recharge VERY quickly.
The Ridata 1GB card is available online for right around $200, which compares very well with the "slower" cards such as the SanDisk. I'd get the faster one since, all things being equal, the faster card is more "future proof" (if you get a better camera in the future it won't be the bottleneck!)