BTW, we made a snug-fitting cover similar to the ATN sleeve out of a microfiber polyester shower curtain and 28' continuous plastic zipper. Clip the spi halyard to the grommet at the top, start the zipper, and pull halyard with one hand while holding zipper with the other. I'd stop every 5' or so to snap a ball bungy around the assembly just above the sheets. Totally eliminated billowing or chafe. Performed this task on a mooring in 35kt winds, many times. Added maybe 4-5 minutes to putting the boat to bed. The cover lasted two seasons in some of the most brutal UV and winds you can imagine, with no harm to the sail; then the material got fragile & started to tear a bit. We'll cut up another $12 K-Mart shower curtain and re-use the zipper. I'm afraid the two grommets are a write-off.
Sunbrella has excellent lifespan, good UV blocking, and lots of colors if you like that look. But it is too heavy for smaller sails or light conditions. UV dacron is still a sacrificial material, and it will need to be overlaid or replaced every few years. That's a fair whack of time and/or money. The advantage of a sleeve is that it does not change the sail at all and can be replaced when needed w/out involving a canvas shop or sail loft. They do add a bit of work, tho, and on windy days it is easier for two people to rig it. (Unrigging it is stupid easy, right down the fore hatch it goes.) Another benefit of the sleeve is that it helps contain the rolled genoa and prevent it from opening on a mooring or in a slip during a storm. Yes, positively cleating the furler line and maybe putting a couple bungies around the genoa will accomplish much the same, but it is another line of defense. May add a bit more windage; not much.