I'm pretty sure you do not need TLAD to download TBOGT. TBOGT seems alot better value than TLAD though. TLAD was good for such a cheap price, but seemed abit dry. TBOGT seems more San Andreas like, with dancing, stupidly odd - yet fun vehicles, and alot more things to do when free roaming.
One thing i would like to ask yo those of you who have TBOGT. Are you able to customize cars? The reason i ask, is because on one of the trailers (the first one i think), there is a shot of a car zooming past with flames out the back, but not like the quick spit like on the banshee; more of a constant flame like on San Andreas when you fitted nitrous. Any of you able to confirm?