I think the main difference between Yamaha and Roland has a lot to do with what and how you are playing...

Yamaha, IMO, is exceptionally good at doing background music, music that isn't 'in your face', grab your attention stuff. Roland, OTOH, have a VERY 'live', 'look at me' kind of sound, and doesn't do polite, polished stuff as well.

How each of these work for you depends VERY much on the venues and types of music you play. I would certainly have a harder time playing background stuff with my G70, and (strictly my opinion) I would have a hard time getting the Yamaha to grab the audience's attention the way the G70 does. It isn't just a question of volume, it's just how much 'snap' and attack and dynamics the Roland's drums have. Great for forefront, not so good for background...

Different strokes....

Anyway, somehow we all manage to make them work for us, and that's what's important