If I was to build a gun it would be without a doubt a dual port. Using the dual port is like running machine gun, only you run rounds down the range with extreme accuracy. The right hand works the bolt and the left hand feeds. You keep your head down on the gun and just run them through. I found that in switchy conditions, I could get off almost all my rounds in the same condition. The only problem I saw with the dual port was if you build a magazine, and have it on the left side of the rifle, it can interfere and get in the way of windage, and elevation on the rest. If you ever have the chance to shoot a dual port gun do it, for it will totally spoil you for anything else.

I would not even consider a right bolt left port. If your shooting off the bench right handed, the smallest part of the bench is the left side, so all your brass ejects out on the ground. If you build a catch box it is in the way of your adjustments on the rest. Also interferes on seeing flags. I realize that some fellows like to remove the ejectors, and I don't know why they would do such a thing. I follow the old benchrest saying "If the brass is not flying, your dieing." It just slows down operation too much, to pick the brass out. Most people that like the left port seem to like picking brass out.

If I was to build a right bolt right port, I would not even consider a target action over a standard action for the extra dough, to me it don't make sense. On a right port right bolt gun, it don't work as fast as a dual port, but your brass can stay on the bench, you have room for a catch box/magazine, and it will not interfere. This would be my second choice over a dual port.