I went Gallagher as he's shown to make a decent fighter out of seemingly average talent. None of them have that je ne sais quoi. McGuigan is known only for Frampton and he hasn't seemingly changed any facet of his game. Booth's main fighters are Haye, Groves and Lee and you imagine they'd all achieve the same or more without him. Gallagher needs more time but I don't like that he stills trains people like Paul Smith who comes in out of shape. He mis-represents what his coach can do.
I definitely agree with what you say about Booth. Certainly about Haye and Groves - Andys success is down to a large element of lucky timing IMO.
I would also add Dominic Ingle to the list. Although probably not the strongest Ingle stable of all time, they still have Kell Brook (IBF Welterweight champ), Kid Galahad (although currently serving ban), Bob Ajisafe as well as several unbeaten talented youngsters such as Jordan Gill looking at progressing within the ranks.
its close between gallagher and booth both are very good, Gallagher certainly has the best stable of fighters than any other trainer in the UK. Mcguigan is still very young and new in this trainer game but he has big potential. Trainers I think that are overrated/ that I personally don't rate - Tony Sims, Billy Nelson, Anthony Farnell,
Robert Mckracken for me Now Froch has retired wonder if he will help another top pro in same way he looked after Froch
Rob McCraken is performance director at GB boxing so could maybe see him taking a top performer from the GB Olympic team into the professional game.
Peter Fury seems like a good solid trainer but out of the 3 above i would say Booth, even though he is annoying and smug.
Definitely Paddy Fitzpatrick, brother. Great taste in Trilby hats, and orange bandanas, brother. P.S Nick Halling compared Oliver Harrison to North Korea.