Well, I hope we don't have to duplicate the old sound debate here on this forum as well, but here is my personal opinion/preference on the subject:
I don't like the loud exhaust because it makes me want to beat someone over the head with a stick.
I generally don't like the feeling of wanting to visit physical violence upon anyone, so I prefer to stay away from people with loud pipes.
Few things are as quick to anger me as a dude with super loud pipes in my vicinity, especially if he's wearing earplugs (I can usually tell because he's usually not wearing a helmet).
This tends to go hand in hand with dudes spraying rocks from their back tires all over the paint job of my $60k truck.
It's usually the same sort of person that enjoys loud pipes and pulling donuts in the parking area.
Also, loud pipes are one of the things that anti-ORV people use as leverage to try and shut us down.
That might not be a big deal on the dunes, but people with loud pipes don't just stay on the dunes, do they?
They also visit ORV parks near hiking trails, and public lands near where people are trying to have a quiet lunch on their back deck with their cats.
Anyway, that's my two bits worth. Shutting up now.