I use a xs3 and it's good for the money and i like it but if i was to buy a new radio i'd definately go for a 2.4GHz,i think it'll become the new standard eventually,or i'd atleast get one that could take a 2.4GHz module,just depends how much you want to spend.
For racing i'd get a Nomadio Sensor,in this thread(page 4) Batfish was telling us about his and it sounds awesome
http://www.rc-monster.com/forum/show...=&threadid=957 plus it's software is updated via download,and it gives you live data via vibration and beeps which you can actually make sense of while driving,for high temps etc.
If i didn't want live data,i'd get a JR Z-1 and a spectrum module(if they make one for it)
Edit:actually no the KO EX10 helios is cheaper and the same except it's not synthesised which would be a waste if you got the spectrum module for it,there is one for it i just checked.
I think the Spectrum DX3 DSM would be the best choice if you don't want to spend so much,it seems just like a xs3 but with 2.4GHz,and it doesn't cost much more than a xs3 either.
To be honest,the DX3 has all the features i'd likely use(apart from too few model memory) so i probably wouldn't bother with the Z-1 or similar high end stuff except for competative racing.(you can just use a little thing called throttle control instead. lol).