I love my Bryston 4B3, but it’s 3 generations newer than the 4BST your son is considering. I also loved my old Bryston 14BSST (one generation). Unfortunately, I haven’t heard the ST, but it sure had a good rep. And Bryston service is legendary.
On the other hand, I have a friend whose system includes an Aragon 8008 (older version) combined with much costlier components, and it sounds great.
So I don’t think there is a clear answer to your question, and I bet your son will enjoy either one. I do see your son is a bass player, and Bryston amps are typically cited for their excellent bass control. For that reason, for their typically great sound, and for serviceability into the future, I would lean towards Bryston.
On the other hand, I have a friend whose system includes an Aragon 8008 (older version) combined with much costlier components, and it sounds great.
So I don’t think there is a clear answer to your question, and I bet your son will enjoy either one. I do see your son is a bass player, and Bryston amps are typically cited for their excellent bass control. For that reason, for their typically great sound, and for serviceability into the future, I would lean towards Bryston.