I have a 250r and I have owned a Trx450r. The 450 is ok, but I would rather have a 250r. They are more nimble and snappy.
Get a 250r and don't look back. The banshee is great in its own rights.
ESR is still developing new parts for te 250r so if you think you can find parts for a 27yr old machine don't worry.
Adam