If you will be grilling, rib and loin cuts are best for high-temp, fast cooking, as they are already very tender. Less tender cuts from the chuck (shoulder) and round (rump) benefit more from low & slow cooking.
Porterhouse has more tenderloin than the T-bone, thus it carries a bit higher retail price, with both, of course, having Striploin on the opposing side of the bone. A Striploin steak, in itself, is great for grilling as well.
I prefer bone-in, even with ribeye, as the bone adds to the flavor of the meat while cooking, as does inter-muscular fat (marbling). I now have no personal preference between the loin or rib...ribeye was my favorite, though the rib and loin cuts are all very good eating off the grill. I will say that the ribeye does seem to have a bit deeper flavor than loin cuts, probably because it is not as lean.
To get some really great detailed info on the various primal cuts of beef so we can make more informed decisions on our meat selection and how to prepare and cook it for the best eating, Pops6927 posted this link:
http://www.meatshop101.com/beef ...in this thread:
http://www.smokingmeatforums.com/t/122288/beef-101
Eric