I have owned both (3B, 3B-ST and 4B-ST)and prefer the 4B-ST. It sounds slightly better and has much greater power reserves. Also, the 4B-ST runs quieter at idle. Brystons amps are best left always running and the 3B has a fairly loud transformer 'hum' at idle. The 4B also has a hum but it is much quieter. I've owned four Bryston amps over the years (the three above & a 5B-ST)and they are a terrific value. Lastly, Bryston service is among the best in the industry and their products carry a 20 year transferable warranty.
