Hi qtm1,
It all depends on what you want to do with it. What kind of music are you going to make with it? The Trinity or the Triton are both powerful synths and can do a lot. The Triton has the added bonus of extra polyphony and you can add RAM to it for sample playback. While the Trinity has a sample option, that sample option is very limited IMHO in comparison to the Triton.
The 2 are very similar yet I find the Triton a bit more on the synth-based side while the Trinity (I own one) has a few more bread & butter sounds. If you are considering a module and a keyboard, I would suggest maybe getting a Trinity and a inexpensive module like the JV-1010 or something like that. This will give you a lot of sound capabilities. Of course, if you are into more synth-based music, then a analog-modelling synth (like a Virus or Nord Lead) might be what you want. You may be able to pick one up used for a good price and then you could get a Trinity as your controller keyboard.
HTH,
Fernando