I'd disagree. He makes some good headers but consistency doesn't match those.
Keane has gotten a lot better aerially too during his loan spells as he got stronger.
Blackett has no consistency on headers, you'd never see Thorpe shrugged aside like Blackett was at "Lester".
I think you suggested before Keane is stronger in the air, I watched him in his pre-season run and didn't notice that, but then he didn't have a lot of headers to deal with.
Neither did I see more than highlights of Keane last season, so you would certainly know better than I how much he improved last season. Didn't really see it in pre-season, again, but he was in a new position as well, in that back 3.
I think Thorpe has been very consistent, personally, but that's opinions for ya.