I have owned both the Xray and the Ta05ms. Both great cars, I sold the Xray though as I prefered the Ta05ms. I still run it, its near indestructable. with about a years racing I have only broken one upright and one C-hub.
As has been said the car's drivetrain is very smooth. I race on a tight circuit and the cars motor postition gives me a lot of speed into the corners.
spares are easily available as it uses lots of std tamiya parts and the car is still being produced (its especially popular in Japan).
The E4 looks great, I flirted with one of these as they look really innovative, but as I keep winning with my Ta05ms I dont see the need to buy anything else atm.
TRF419, TBEvo6, TT02, VDF, TRF501x, TRF201, TRF101, Mi5, X-Ray T4-13, BD7 2014, A700 Evo, WR-02G