To me, mouthpieces are like masks to some degree-- Highly personal in terms of fit, comfort, etc.
My first regs had an Aqualung Comfo-bite mouthpiece. I hated it. If my jaw was kept slack, the weight of the reg pulled the reg down and pushed the top of the mouthpiece up so that it rubbed annoyingy on my palate just behind my upper incisors. I gave it a few dives, but got rid of it as there was just no way that I could get comfortable with it. I know lots of people that swear by them though.
I have found that I prefer a mouthpiecs with longer bite bite wings. To others, these are just as (or more) uncomfortable as I found the Comfo-bite. Just in a different way.
I have loved my Sea-Cure moldable mouthpieces for a long time now. Sea-Cure does have the option of trimming off some of the wings prior to molding to give a much shorter bite wing. We had to do this for my daughter's reg set.
Same advice for mouthpieces as for masks-- find the one that works for you and are comfortable with. Be prepared to potentially try a few. Thankfully, there are fewer mouthpieces to have to cycle through than masks.