The Primus clip-on windscreen is mostly open and isn't much of a windscreen.

There isn't a vast weight difference between a small gas burner and an alcohol stove, but there is a vast difference between the wind protection of something like a Caldera Cone (very good) and a Primus clip-on (particularly poor). There are other windscreen options for small gas burners that will give you better coverage. I've got some listed on my blog: Windscreens

I've seen a lot of different sets of numbers from guys doing actual cooking on the trail. In general, the break even point seems to be about 5 to 7 person days. If you're out for less than that, an alcohol stove is lighter. If you're out for more than that, a gas stove is lighter.

But they're pretty close. Some of it comes down to personal preference, and just how much emphasis you put on weight. There are "gram weenies" out there for whom a 10g difference is a big deal, and they're willing to do the work to shed those 10g.

Alcohol stoves generally fit my approach to cooking while backpacking (KISS), and I like that the Caldera Cone is efficient and consistent.

Small gas stoves excel in speed, flame control, and convenience, but they generally suck in wind. The Caldera Cone excels in wind. I was camped a couple of weeks ago at 10,500'/3200m. It was windy. I was really glad I had brought the Caldera Cone and not a little gas stove.

HJ