I'm sorry, but this is just wrong on so many levels.
For one thing, Mr. Smith has had a mere one hour of screen time as the Doctor, compared to Mr. Tennant's three full seasons, which hardly allows for a fair comparison.
For another, David Tennant, it would be fair to say, was hugely popular as the Doctor, probably more so than any other Doctor since Tom Baker (possibly more so than Tom). Which is likely to skew the results more than a little.
For another, if you're going to conduct a poll to see who's the better Doctor, why not include all of them, from William Hartnell onwards, rather than limit it to the latest one and the current model?
For another...why would we want to choose? I loved David Tennant's take on the Doctor. So far, I'm loving Matt Smith's interpretation of the role. I couldn't, in all honesty, say that one was particularly better than the other. On the whole, I favour the Brigadier's policy on this one. The Doctor. Splendid chap, all of them.
Re: the userpic. I would use my animated "Giving Monsters Nightmares since 1963" pic, but it needs a bit of updating...