[user104658]

Brian I think wasn't really given enough of a chance - he was inexperienced and had VASTLY improved from the first series he did (he was awful and very nervous then) and might well have improved year on year. That said, I'm pretty sure he was axed for budgetary reasons; too expensive to keep both him and Emma on as her pay has probably been increasing.

Davina was far superior to Emma though. Emma is a great BBBots presenter, better than Davina was when she tried her hand at it, because Bots is supposed to be very informal / just a bit of a laugh... but Davina was the better main show presenter by a mile. More professional, usually unbiased (though she had her moments...) and a much stronger interviewer. Maybe Emma will improve with time? I don't know. Her established persona just doesn't translate well into a proper interview.