I only saw one episode of Eccleston.
Didn't like it. At all.
Tennant is my Doctor, the first one that I saw. LOVE Tennant's Doctor. I saw an interview with Smith, who said something to the effect that he loved Tennant's quirkiness with the Doctor and how he would like to emulate that.
In his words, about following Tennant, "Those are some really big shoes to fill, and I hope I can live up to that."