The Bach 5G has been the most used mouthpiece by professional orchestral trombonists for decades.
The tone is full and rich, the articulation light and clear. However, it needs a strong, well-developed embouchure and takes a lot of air.
If you don't play often or don't play in orchestra, you may prefer a shallower mouthpiece that is not such hard work and has an easier high register.
I have a few 5Gs of different vintages and the brand new one I just bought is the best.