Subjective. MAY block the trigger guard. MAY be slower. The heel of the support hand thumb MAY impinge upon the slide release, and that MAY be eliminated or at least mitigated by pushing the support-hand thumb downward toward the index finger.... Saying it WILL (for any of your PRO/CON lists) is akin to creating a self-fulfilling prophesy, so make sure you're looking at it from the perspective of asking yourself questions, not making statements.
Of course. I meant in my current experience. I've yet to do anything but dry fire with the higher/forward grip (Costa-style?), and I'm experiencing this. As you stated, I agree: it's a simple as training away those bad habits before they occur.
A good look at it the latter method:
http://pistol-forum.com/showthread.p...AR-01-Nov-2012
This is surely not what you're looking for, but the answer is "Both, and neither." For example, saying that the former will produce a less-dominant grip isn't a valid stand-alone statement. Your hands aren't my hands, and vice-versa: size (length/breadth/girth of fingers) of hand, shape of hand, grip strength, type of gun...all of this will have an impact in regard to how and why you establish your grip thisly or thusly.
Example: The way I grip a Glock or M&P differs from the means by which I may grip a Sig or HK, simply on the basis of the differences in the placement and shape of the control features. Read any of Todd's handgun endurance tests, and you'll see him speak to grip tweaks for those reasons and others that have more to do with raw performance enhancement.
Sounds like a great excuse to SHOOT, and find out which of them, or what blend of the two, work for you.
Wait, what?!? I have to shoot more?!? Oh, no... how unfortunate. (Now, to show my wife this.)