Three times a furler...
I am on my third boat with inmast furling and never had any serious sort of jamming incident. I also club race and know that reduced sail area means a poorer sail area displacement ratio...in light winds only. The fact of it is we have pretty steady and lively winds here in S. Tx, so the hanked up mains have to be reefed, usually on the worry that winds will hinder. Often times the winds don't rise as much or if they do they then lessen at times. The reefers pretty much stick with the original choice. We furlers keep full longer and revert to full more readily. We end up having more SA/D because we can. So we are always competitive. But there are other factors in the deal. Displacement can be reduced. Take out all those cans of Dinty More stew, gallons of water, full fuel tank loads, and all those cute things you stuck away for "later". Put on a folding prop...its a good deal even with a handicap adjustment. Finally, drill your grinders, sharpen your helmsmanship, smooth out those tacks, deploy the whisker, and trim, trim, trim with the traveller, the sheets, the sheet cars.
In the end, the reduced sail of a furled main may be only a smallish factor at all. AND NOW THIS: They have battened, roached furled mains now, so even that disadvantage is fading.
Finally, I solo sail more than a third of the time. When I'm out in the ocean in six footers, fooling with a mainsail on the top of the cabin is going to do one of two things: make me think twice about going out at all, or using up one of my n lives.
I'm always going to for the furled main...