Yet, what would I rather choose?
1. A tanker that has more range, and fuel offload but requires some minor changes to existing procedures (for certain aircraft only) or
2. A tanker that has less range and less fuel to offload but adheres to all current procudres.
Thats far from the truth.
1) Sure the A330 carries more fuel on takeoff however it also consumes that fuel at a higher rate. So the A330 has roughly 30,000kg extra fuel at takeoff than the 767. If it uses half of that fuel due to the extra weight/drag of the larger airframe it may translate into only 15,000kg of extra fuel for the fighters.
2) More 767 based tankers will be able to be purchased due to their cheaper purchase costs and operating costs. If the 767 carried 30% less fuel but you could afford 30% more aircraft then the 767 is the better choice. The better choice because you have just as much fuel in the air but a greater number of locations for pilots to refuel. However it seems the 767 isn't 30% cheaper to make up for its lower fuel capacity, so it is rather even comparison.
If they choose the KC-45 they will get more fuel in the air but they can only be at so many locations at once. Having fewer KC-45's they will have to be spaced further apart so fighters will have to travel further to refuel.
I'd much prefer 5 KC-767 tankers in the air, supporting my air campaign than 4 KC-45 tankers.
IMO if the USAF with a set budget could afford more than 15% extra KC-767 tankers, then the 767 should win. If only say 10% more KC-767 tankers could be purchased for the money then thats not enough aircraft to make up for the lower fuel capacity and i'd go with the KC-45.
You can alter the requirements to give an advantage to either aircraft.