I started with David Tennant and at first I really, truly, utterly missed him.. more than words can say ^^ And when I saw Matt Smith for the very first time it was kind of like raising one eyebrow and thinking "Really??"
But now I have to say that Matt Smith has become my favourite Doctor... but he shares the title with David Tennant.
Matt Smith himself, he IS The Doctor. I mean, he's intrigued by badgers, otters, and llamas.. That's so Doctor-y.
By now, I totally adore Matt Smith's impersonation of The Doctor and I even got more addicted to DW ^_
I started out by watching the Eleventh Doctor, but I soon sped through seasons five and part 1 of six, so I went back to the beginning of the series. I was never quite so taken with Eccleston's portrayal of the Doctor, so the introduction of the Tenth Doctor seemed like a blast of fresh air.
So yeah. In the end I have to go with Ten, and it's not just because of my slight obsession with David Tennant's hair, although that's probably part of it, hahaha. I love Eleven, and he has me convinced that he's really the Doctor with his lovely, eccentric personality, his hinted loneliness, and with his liking of the human race. But he seems to me to have this air of invincibility around him, whereas Ten, while definitely immeasurably more capable than the average life form, actually seemed to have real weaknesses, however difficult they may of been to penetrate. In the end, I feel that it's this slight vulnerability that has me a bit more attached to the Tenth Doctor than to the Eleventh.