I am SO not a RS4 fan. =) So My opinion is going to bias.
NTC3 RTR can Go faster than the RS4 RTR... I think
The NCT3 parts are somewhat less costly.
The NCT3 does not run on a stupid belt that I totally dislike... BTW Can that belt snap?
Correct me if I'm wrong
Eh.. Thats my 2 Cents.
If you want to see a NTC3, follow this link http://community.webshots.com/album/63076019mVYhqT
Thats my car. A bit on the ugly side, but I can live with it.