bandphan is right, they are two completely different technologies unlike LED vs. standard LCD... whereas the form of lighting is the only difference. As far as refresh rates go.. LCD uses extra frames in between frames to get the higher 120hz refresh rate whereas plasma flashes dots during each frame (60 frames+10 flashes during each frame=600 hz).
The numbers mean nothing with plasma. A 48hz plasma won't have motion blur issues like the 60hz LCDs. The LCD folks keep uping the refresh rates to smooth out movement that even earlier model plasma displays didn't have issues with. The 480hz is next, just another way to fool buyers into thinking they are getting a better display because it has a higher refresh rate.
This is all really kind of irrelevant to the OP. The person was looking for a midpriced 52", when the "LED is best" attitude came about. Not too many folks are gonna agree with ya there, clouso, when there's better displays for less money. You are satisfied with your toshiba and that's all that matters but don't expect folks to pat you on the back for spending 3 grand when you could have spent half that on a display with better pq. I surely wouldn't be promoting it in this thread. I'm sure the poster has seen the LED on the showroom floor if he/she has been looking at any electronic store....they are heavily pushed if you haven't noticed lately.