They're both very good.
There are a number of agents on Northcote Road that I hear are truly awful and you haven't picked one of them
We sold our place through M and P and they were very professional, although a lot of that is who you're dealing with.
A good friend let his place through RB and he was really pleased, felt like they did what they said they would and that, compared to some others, was a real plus point. The people he felt were really awful you haven't named!
I'd go with whoever you feel most comfortable with. Neither sound like they're going to be the wrong decision