Ion by far the best option.
Ir3 - stock, youll get about 9bps tops, in semi ONLY as there are no modes. Youll chop paint as there are no eyes and the COPS system almost always sucks d1ck. Youll get a nice arm workout though as the beast weighs a lot.
Youll also have to charge the battery in your car or shell out for a wall adaptor (>£20) which is just plain annoying.
Ion - stock , youll get 17bps in semi and ramp modes. youll get breakbeam eyes. its light and small, and runs off 9v batteries.
Its cheap and cherful and you can break it if you take it apart like a gorilla wokring on a bunch of bamboo shoots. but take care of it and it will be far more useable in a supair situation than an Ir3. budget ~£60 for upgrades from your stock setup (trigger, barrel, feedneck).