I cant speak on the mugen, but I do own an RC8T CE. Here are my observations with this platform:
Pros:
Handles excellent on all tracks.
Easy to dial/tune for any track situation
Lots of hop-ups and parts (all of which are affordable)
Lots of steering
Cons:
Worst plastic ever! When tightening screws, you cant feel the end, its really easy to strip a hole.
Rear hub carriers snap like crazy if they are plastic. Its due to the fact that the pin is 3mm and should be 4mm. Can be modded though. That or buy the 65 dollar aluminum hubs.
Camber links and steering links like to crack.
Fuel tank dont like to stay shut either, you may have to buy slightly larger o-ring for the lid to get a good seal. Mine is constantly leaking fuel even if I physically push down on the lid.
Drive shafts are brittle and will snap after a few gallons.
That said, even though there are alot of cons, I really do enjoy driving this truggy. It handles great, and with the right motor, its super fast. I dont bash in parks and only drive on tracks. I am not hard on my vehicles.
You will have to figure out if you want a superior platform for construction ( mugen ) with more expensive parts that are replaced rarely or go with a platform with inferior construction (poor plastics) but are cheaper to replace, but will need replacing more often.
I guarantee that if you switch, you will like the RC8T, but you wont like the pastics and the fit of the parts compared to the mugen.