These guitars aren't for everyone. But I like them. I've played several McPherson's and like some more than others. Some really put out and others less so. I've only played one Batson and found it thin sounding next to most McPherson's, which I played in the same sitting. I own a Tom Bills Genesis and like it very much. Tom built it for me in 2004. It's got a tone that is kind of a combination of an archtop and a flattop. Tom builds some amazing archtops, and you might want to check those out as well. He has a hybrid, with an arched top and top sound hole like a flattop. He's not shy about experimenting.
To answer your question about the sound hole and doubling the area of the soundboard vs volume, no it doesn't make the guitar twice as loud. With the sound hole on the side, I think what it mainly does is put the sound right in the players face. It's a wonderful sound and it's a great thing to get that kind of feedback as you play. I've played guitars that were uninspiring as I played them but out in front, the sound was amazing. I think the side sound hole design puts the player in the front row. It's very cool. It's got a delicious bass response, as well.
Some photos of mine and a few recordings.
http://www.davidhilyard.com/downloads/Spindrift.mp3
http://www.davidhilyard.com/download...er_is_Wide.mp3