Glen,
actually Propane produces more heat per ounce than Butane. http://www.exothink.com/Pages/btu.html
The can the propane/butane/iso comes in weighs 5 or 6 ounces, and that is non-consumable weight. You can now buy a titanium remote canister stove for a fraction the price and weight of a pocket rocket. The problem with a "sit on top" stove (I have used them many times) is that 1) they are not very stable, and 2) it is my experience that the canister gets cold in snow and slows down considerably in spite of the Propane mix. With a remote fuel set up you can warm the canister with your hands and snap it back into life, or use it inverted so there is never any problem with cold. Nevertheless, when I am not trying to cut ounces (like on an easier or shorter trip) I take my WindPro (6.9 ounces; heavy) and a full canister (13 ounces) and it is a workhorse, windproof (with screen) and fast and works independent of the weather. It can easily cook for two or three people because it is so fast and efficient.

Of course, as usual, it often comes down to personal preferences, experience and what you are after. Too many random variables perhaps.