I may be a bit late to this party, but I would suggest, no matter which carry position you choose, that you personally try out a few different ones. IMO, a holster is one of those personal choices that it is hard for someone else to make for you. For instance, I'm not a fan of nylon, or clip-on holsters, but a buddy of mine, who is highly competent himself, likes both. If you have a local gunshop, or range, you may talk them into letting you test drive a few models. You may also find a buddy who will let you try a few of his. Good luck, and sorry for not having a clear answer for you. I'm just not sure this question has only one answer.
I also agree on the shoulder rigs being hard to access in most instances, and in having a dedicated and accessible spot for your weapon in the vehicle. You can even dedicate and attach a holster in your vehicle just for that purpose. IWB is my preference for most instances, but to each his own.