I don't know about the TTR, haven't ridden one. I have plenty of time on XR100s, and you generally can't kill 'em, and there's lot's of hop up stuff for 'em.
I did ride a CRF150 and was very impressed with it. more bike than the XR100, but I don't know how modded it was, I suspect more than somewhat. Even still, between the two Hondas, I'd probably go for the 150...I think it has a bigger frame, and better suspension components.
How much money?
grab the crf. i think itll be worth it in the long run. there is as much stuff available for the crf as the xr's now. big bore kits, etc... what are you going to do with it? thats the real question. our short track races dont allow 150's i dont think. and weras limit i think its 120cc. so it was a no brainer.i dont know that id buy a crf unless it was the r model, you know, the expert, that and i love my 100. im not sure what the differences are, but after riding the 150, i can tell you it feels really different. i havent ridden one of the r models yet but im sure they are insane. do youreself a favor and get the suspension upgraded. and buy yourself some rear spokes. youll need them. so id think buy the 150, but im a xr fan myself. they are both really similar in size etc. so no worries there really. get a pic when you pick it up. not such a big fan of the ttr. the l model is electric start. heavy. for 1k the xr should be in pretty good shape. like real nice.
"tex, if your bikes a cheater, its not a very good one"