This is an impossible question to answer given the lack of information about your preferences and priorities. Are G&H good? Yes. One of my dinner suits was made by them. Do I like it? Yes. Why do I usually go to another house? Mostly because the "vibe" and guys at the other place suit me better (no pun intended) and because we share a similar sense of aesthetics. Because I enjoy having a few pints with the boys. Because I honestly enjoy having brunch on a Saturday with the guv'nor and his child. A completely personal choice that is not based on technical merits at all. In fact, discussions about who is "better" is never productive or indeed relevant. Are the guys (girl) at G&H unpleasant? No, perfectly pleasant. Good for YOU? No idea.
It's a bit like asking whether X is a good restaurant. Yes, if you like Ethiopian food. If you happen to be in the mood for Ethiopian food. If you are not vegetarian. If you don't mind sitting on stools. If you don't mind eating with your fingers rather than using cutlery. If, if, if...
Someone mentioned cachet. That is also a notion that varies from person to person. Is it the sort that one might associate with Poole? Is it the sort that one might associate with Hart or Boateng? Or, is it another sort? Only you can answer this.
You should visit a few places, talk to them, explore and decide for yourself who is right for YOU. That said, as I'm sure your brother has already mentioned, do keep in mind that many respectable houses are shut at the weekend unless there is a specific appointment with a client.