When you say "recently," do you mean this is your first time watching Doctor Who, or had you seen any of the older episodes in the distant past as well?
Of the two actors you mentioned, I preferred David Tennant, though that’s not to say I have anything against Matt Smith. They each bring a different energy and personality to the role, which I think fits perfectly with the nature of the Doctor. After all, with each regeneration, the Doctor comes back with a new face and a new personality, so that variation feels right to me.
David Tennant definitely became a fan favourite, and I think it’s easy to see why. That said, I grew up with Tom Baker in the classic era -- or at least the repeats. Along scarf, wild eyes, a completely different vibe, but iconic in his own way. He was the Doctor to me for many years.