WEll its difficult to say which i like better sincei have been running TC3s for years but of course the SD is new and shinny so my heart say the SD is better.
I feel it drives similar to the TC3 and i also feel they share very similar plastic quality. Meaning i think both will break if abused without a bumper.
Hands down thoug the SD is simply easier to work on. I was shopping for a new car and did not want belts for many reason but the main reason is the BS involved with getting at diffs for service. To find a replacement for my TC3 meant the car had to be as good or better and easier to work on. The TC3 is easy to work on but the SD makes diff and spur gear service easier. Also i feel the cells sit lower in the chassis then with the TC3. I had looked at the EVO3 but found i did not like its diff gears size lifespan as well the center line of the drivetrain did not seem to have as much bearing support.
I think its hard for AE to top there TC3 into a TC4. I think they hit a design thats hard to improve on wihtout going to the graphite chassis route. I think thats why this car has had such a long life span. How old is the TC3 now? HPI has been through 3 models and Tamiya 3 or 4 in the same life of the TC3.
To answer your question. The yokomo is my favorite!
IT just does everything better and looks much nicer!
RAce 3 on this car is thursday for me. Ill try the oneway this time