I just switched from the Triumph to the Exhibit last weekend. I'm glad I made the switch. The screen is terrible on the Triumph. It misses taps half the time and back button works after about 4-5 tries. Its a common problem among those phone. The GPS takes ~5 minutes to lock on. The battery life is not good. If you do get the Triumph, root it and install FroyoCream Sandwich right away. Its a lot better than the stock ROM and everything works, not like in CM7. With all this being said it is still easily the best phone on Virgin and still a decent phone in general as long as you are able to live with the quirks. It took about 8 months for me to get fed up with them.
The Exhibit is perfect size IMO. The two phone have close to the same specs except the camera. Even thou you get a 5mp on the Tirumph the photos are no better than those on the Exhibit so I consider it a wash. The battery life is way better on the Exhibit. I went over a day yesterday with moderate use. Triumph will be dead in 12 hours. The biggest improvement is the responsiveness of the Exhibit screen. Its exponentially better than that of my Triumph and probably the biggest reason I am happy I made the change.