I'd describe it this way.

Eccleston and Tennant give star performances.

They are essentially themselves performing the role as themselves (even if you factor in David's slightly dodgy accent).

Eccleston silently fuming as the Doctor is pretty much like Eccelston silently fuming in any other role you may have had the pleasure of seeing him in.

Tennant's Dane is Tennant's Doctor with a more interesting script.

There is nothing wrong about this, some of the best loved Doctor's were essentially the actors just performing the scripts as themselves.

Hartnell's Doctor was a slightly amped up version of the man himself by all accounts, where as Tom's Doctor was Tom slightly toned down, if you can imagine that.

What you get, which is actually rather remarkable and was totally unexpected by myself when I first saw it, from Matt is a character performance.

It's like all ten previous incarnations of the Doctor (plus a bit of Matt Smith) are all under his skin and fighting for voice at the same time (with second Doctor getting the upper hand).

If you see Matt play someone else it's not the same.