Only converted into a Dr Who fan after watching Matt Smith, love his quirkyness. Not sure what David's appeal is, probably because I havent watched a lot of episodes with him in it. XP
Back when the Doctor still had some vigor. The Matt Smith Doctor seems so tired and ready for the end, also is reverting back to his bland pacifissm; not that he has not had his moments.
Here is the issue with comparing them, they are different characters with the same history. I love them both for different reasons. I love David for his intensity, and he is really scary when he is angry. I love Matt for his love for life, his enthusiasm for his adventures. He is really sneaky and smart, and he is, while not as hot as David, far more lovable and playful.
I like Matt as well but David just nailed it. He was also a HUGE fan of Dr. Who when he was a kid so I think thats probably one of the main reasons why. Also he maried the man who played the 4th Doctors actual daughter.
I like smith for not being very serious and I like Tenant for being somewhat serious. They both had really interesting approaches toward the character and were attractive. I can't choose between them.
Sorry, Matt Smith wasn't doing it for me.