On number one drivers
The policy at both McLaren and Red Bull is to treat their drivers equally. But in moments of stress, the people in those teams will pick sides.
I think that's all that happened at Red Bull last year. There was tension on track, there were almost certainly rows behind closed doors, and people find that really hard to sort out. To an outsider (me), it looked like they favoured Vettel, but on the inside, they were probably just wishing it would all go away and saying what they thought would calm the drivers down.
On the best place for Hamilton
I believe that what Hamilton needs is to become a better, more aware person. If he does that, he can become a more effective driver - judging risks as well as taking them.
I think (hope?) he's started that transformation. Since the departure of Ron Dennis, the split from his dad and the arrival of Jenson, he's got a much better group of role models around him. So if I had his ear, I'd suggest he stay put. Still, Red Bull seems a happy place, and Christian Horner is a level-headed guy who has done well at nurturing Vettel. Perhaps that would work out too.