it is always good to invest in a good radio, especially if you race.
the JR X3S is a good radio (in fact that's what i'm using right now / that is for now
), no problems with it... it not capable of switching to 2.4Ghz band though.
the 2.4GHz band gives you the convenience of not worrying with frequency checks and the crystal sets. you sometimes worry if someone else maybe using your freq and you do frequency checks in the track
there are also better radios out there that you may also find interesting, i've list a few which IMO are the best Radios out there for now and not in any particular order, all of which are FM or 2.4 GHz radioset/capable:
Futaba 3PK - FM/systhesized / FASST or Spectrum system for 2.4GHz option
Airtronics M8 or M11 - FM/systhesized / SANWA or Spectrum system for 2.4GHz option
Spectrum DX2/DX3 or the DX3R already 2.4GHz system
Nomadio React/Sensor already 2.4GHz system
i don't know their respective prices though...