I wouldn't buy an LTE phone on Verizon right now, its only a few weeks until the Bionic is launched, and other LTE devices following in October. The current LTE devices are all 2010 phones with an LTE radio and all get lousy battery life.
Of the three though, I think the Thunderbolt is the best choice. Its sturdy, has the most community development, and has cheap on contract pricing. The Charge is a decent device, but its battery life is no better than the Thunderbolt's. Its screen is much nicer, being SAMOLED, but it doesn't seem to have a lot of dev support because the Samsung devs are wanting the SGS2 variants. The Revolution . . . shrug, its the same hardware as the TB, with no dev support, Bing, and LG's a relative new comer to the high end arena.
I'd hold off until September and October, for the Bionic, Vigor, and Stratosphere.