recommend 15 degree or zero degree
I had the same question a couple years ago when I was buying a new paddle. Being the type that has to look up every angle of an issue, I looked up every dicussion I could find about on the issue of the "optimum" feather angle, and I just don't buy any of it--the way I look at it, paddling is a perfectly symetrical activity--a paddle stroke on the right is the mirror image of a stroke on the left, so any advantage gained buy some feather angle on one side will be offset on the other side.
Obviously, things are different for sea kayaking, or paddling out of westwater, but in my experience wind is not a factor for 99.9% of river running and playboating.
I wanted to go with a zero degree paddle, but I would have had to special order one--and CKS had a great price on a 15 degree werner player, so I got it and I've absolutely loved it--very comfortable, and no awkward twisting. That being said, I do subscribe to the "muscle memory" idea, so if you're used to 30 or 40 or 45 degrees, and it works for you, by all means use it.
just for the ease/simplicity factor, I would get a 15 degree, unless you could get a zero degree with having to special order it
that's my $0.02