… and what, pray tell, is so wrong with Tennant?
Nothing! He's Amie's fourth favorite doctor, even with all the emo!

Amie: explain for all us non-whovians
He's just sorta… like… really into vengence. Not super compassionate, especially towards the end there. Did a lotta killing, and/or condemning to eternal pain and damnation.
Always justified, mostly, maybe, sometimes, but well -

- she's an alien.
A real, honest to god alien. The only one, and if what the Bina's and Gregor have said, just a baby, or the multidimensional insect equivalent. She's asleep, and unformed, or unfinished. You don't kill something like that, it's just not right.
It's not how the story's supposed to go.
Notes
1400 days! Woo!