Actually, both are pretty good IMO. Rackshack has fast setup times, and has some solid bandwidth for the price.
My only gripe with Rackshack is I think their MRTG graphs are a bit screwed up. When I had servers with them, and the monthly bill came... the MRTG graphs always seemed to be at least 20% higher than my own estimations using logfile analysis.
Actually because of this very reason I switched to The Planet - which their dedicated server division later became ServerMatrix.
Since switching, the bandwidth graphs always seem to be perfect now, and never have any bandwidth overages like I occasionally had with Rackshack.
Just my
on the issue...