Both the Triton and Trinity are awesome keyboards. Soundwise, there isn't really anything between them (and in fact the filters in the Trinity are more flexible). But Triton has more onboard waveforms, better LFO's (Which sync to MIDI clock), an improved operating system with better touchview screen, slightly better sequencer and 2 arpeggiators, 62 notes of polyphony (the Trinity only has 32), ampling capabilities and multi timbral MOSS sounds with the moss board installed. The effects have also been improved and there are now also 6 freely assignable outputs as opposed to the 4 on the Trinity which had poor output routing capabilities.
If you have bought neither, then by all means look at the Triton- it's extra features are worth it. However, don't neglect the Trinity either, particularly if you get a godd deal on one.