The impression I get is that many of the skills and attributes of a good supervisor are general academic and quite transferrable. They should, of course, have a good general knowledge of the wider subject area but you are the expert in your own PhD. As my supervisor told me, if your supervisor knows more about your topic by the time you complete the degree, there's a problem. Questions to ask yourself, and possibly some of his other supervisees if you can: (1) does he have a good track record in publishing (2) Can he steer you through the minefield of academic life including publishing, teaching etc.? (3) Does he have the time to devote to supervision? Some of the best supervisors on paper are very, very busy people; and (4) What's your impression of how you'll get on with him? Some people may disagree, but I think personalities count when you're trying to build and sustain a positive professional relationship dynamic in a situation like this.

Anyway, these are my two cents - maybe post again to let us know what you decide to do?