Functionally they are the same thing. You get the same options for tunes/parameters to change on either one. From what I hear the trinity has a bigger memory for data logging if you are looking to do any custom tuning, but not by much.
The ability to have the Trinity mounted up on the dash, you get a couple gauges to monitor in addition to what you have on your cluster. As well, with it always plugged in and ready, it makes changing tunes on the fly a bit quicker.
Other than that, I prefer the DCX just because I didnt want to give anyone more reason to break into my truck, and the suction mount that comes with the Trinity doesnt hold for ****. It really comes down to personal preference. And your budget.