My first response is: Huh? How can the fuel “seem” to weigh a lot more, unless it uses some sort of mysterious liquid-lead component?
But, let’s run some numbers, comparing the Pocket Rocket ($40) against the venerable MSR Whisperlite ($60). First, we’ll look at the stoves themselves. The tiny Pocket Rocket weighs a mere three ounces, the Whisperlite, 11. Advantage: Clearly to the Pocket Rocket. Now, the fuel. The Pocket Rocket can run full blast on a single canister for 63 minutes. Weight of full canister: eight ounces. The Whisperlite, meanwhile, can run for 136 minutes on 22 ounces of white gas, which doesn’t include the weight of the fuel bottle. Putting the bottle weight aside, the Pocket Rocket requires .13 ounces of fuel per minute of operation, the Whisperlite .16. The Pocket Rocket burns hotter, too, boiling a quart of water in three minutes, 30 seconds, versus nearly four minutes for the Whisperlite. So the Pocket Rocket requires just under a half-ounce of fuel to boil a quarter of water, while the Whisperlite about .6 ounces.
Bottom line: By any conceivable measure, the Pocket Rocket is the lighter stove. Of course, they’re very different stoves. The liquid-fuel Whisperlite is certainly more economical to run (Pocket Rocket canisters go for nearly $5 a pop; MSR-brand white gas goes for $4.50 for a quart, or 32 fluid ounces.) Also, the Pocket Rocket fuel consists of isobutane, which performs pretty well in cold weather, but white gas is the clear winner for performance when the temperature drops below freezing.