Favorite Doctor is such a loaded question...
They're all the same Doctor, with different faces. And, according to the Banter between Smith & Tennant, different sized *****'. Now least favorite? Pertwee. Not that I though he was bad, but more so having to do with the whole plot revolving around him being exiled on earth & working for UNIT.
Eccelstein would be my next least favorite & again not because of his performance as 9, but mostly because he wouldn't do the 50th. Jerk.
____________________________
"The Rich are there to take all of the money & pay none of the taxes, the middle class is there to do all the work and pay all the taxes, and the poor are there to scare the crap out of the middle class." -George Carlin