Pro, you do realise Tennant is an actor playing the part of The Doctor, and the Doctor isnt real, yeah?

Eccleston, for my money, didnt act, just like he rarely acts.
He just tends to go in and be Eccleston in every role he does, with very little variety.
Just look at his role in Heroes, its almost a carbon copy of his version of The Doctor.

Tennant though, the simple fact that he can overcome a Scottish accent (something Eccleston has never been able to do with his Northern accent), shows to me, that Tennant puts in more effort.