Just like choosing a hang glider that is suitable for your current flying skills and desires is important, the same goes for choosing the right instrumentation.
When learning to fly, all that is really important is you know your altitudes and it's nice to hear the beeping of your vario when you get in rising air. If your instruments are too complicated, it can make learning to stay aloft rather frustrating - information overload!
Once you get basic thermalling down pat, then you can consider getting a vario with toys like a built-in GPS, air-speed indicator, maps, etc. Only then should you consider upgrading.
To see a great comparison chart of Naviter's instruments, see here.