I've read too many horror stories and my friend had one of them, with the Triumph.
I love the Optimus V, but wanted a bit more in terms of a screen and I'm much happier with the $30 100talk/UL/UL plan(5g at 4G) T-Mobile offers.
The Samsung Exhibit II has been great so far. The GPS lock is pretty quick, but I don't think a device will ever match the Optimus V in that regard. The screen's a bit bigger and a heck of a lot sharper. I'm very happy with the Exhibit and would recommend it over any other prepaid option out there.