My cook kit for solo use (boiling water to rehydrate food in freezer bag or for tea):
Primus Micron Ti stove: 2.4 oz.
Ti kettle, 550 ml: 2.2 oz.
Mini bic lighter 0.4 oz.
Windscreen 0.3 oz.
Total 5.3 oz.

Jetboil Sol Ti, per specs on REI website: 9.9 oz. Both weights are, of course, without the fuel canister.

My setup, for my needs, is far more versatile. With my stove I can use any pot or frying pan, take a big pot to melt snow for water, do full cooking or (as I normally do) just boil water. My windscreen is a sheet of Ti foil that goes 3/4 of the way around the canister. It keeps the canister warm in cold weather but doesn't overheat it, and definitely makes the stove more fuel-efficient, especially in windy conditions. It's extremely important when using a windscreen with a canister stove to feel the canister frequently to be sure it doesn't get too hot. An exploding canister could ruin your day!

For some, the convenience of the Jetboil may be worth the extra weight and lack of versatility. "Your Mileage May Vary" definitely applies here!