tri tac is the so called "tactical version" like green said, of the trio. Trio is a nice light for me. slightly dimmer than X5, but there is more actual flood light than the X5.
Whats good about the Trio is that there are few 2 AA battery suckers out there. The single AA battery suckers are just too dim overall for around the house work, and for me, its hard to come by 123s, which is what most good battery suckers run off of, so I like the Trio. It is pretty tough too. I dont think the Tri Tac is worth getting though. But the TX 3.0 sure has me interested.