I switched to 6v in 2004 and am happy enough with them to keep using 6v.
My only advice though is to only use 6v if you have the room and the budget for four batteries (or more). That way if something goes wrong with one of your batteries, you still have a functioning pair that make 12 volts.
This hasn't happened to me in a long time, but twice I've had a battery go bad. The first time we just had two 6v batteries, so losing one put us out of business until somebody nearby loaned us one of theirs for the weekend.
The second time, we had four batteries, so the second set did the trick until I could replace the bad one.