Hi:
I've not flown either sail, but have done plenty of daydreaming, scheming, research, and pricing on the question of a larger, light air foresail. TLDR Conclusion: Stick with the Sym Spinnaker if you have one and otherwise enjoy the ride on the main and small jib. Answering your questions and explaining my conclusion:
1) The term "Code 0" is very loose and undefined. For a racing, code zero for monohulls is often restricted by rule to a mid-girth of at least 75 percent of the foot length and a leech that is no more than 95 percent of luff length. Since both sails are illegal for DaySailer racing, it's a moot point. There's been some rules discussion about allowing Asyms, etc, but the idea is always shot down. It goes against the ethos of keeping Daysailers relatively cheap and accessible for racing - which I heartily agree with. We don't need an "Arms Race!" Anyway, for cruising, there is no real definition of Code 0, so both the "Generator" and the UPS kind of are Code 0's, why not? By the way, both "Gennaker' and certainly "The Generator" are just marketing terms.
2) The UPS is for angles further downwind. The Generator is a reaching Spinnaker or full cut Genoa (take your pick how to describe), for higher angles. I believe it's cut at 165% of the fore triangle and it's luff is free (not hanked to a forestay). The Generator needs a pole to go deep downwind. I don't think that the UPS does need a pole, but it needs a bowsprit to hold it out ahead of the forestay.
3) The UPS is a fractional sail, at least on our boats, so essentially a pole-less (I think) Spinnaker. The Generator is a masthead sail, so you both have to rig another halyard and keep a close eye on your mast bend. Too much wind and that Generator will pull your unsupported masthead forward or to the lee (depending on your angle of sail) with untoward consequences to your mainsail trim.
Which brings us to my own ideas for a "Daysailer Drifter," which would be a crosscut, 155%, masthead "Drifter Jib" sewn out of 1.5oz nylon. With Dyneema for the luff rope (free flying luff), you can use luff tension to move your draft around for upwind or down. The problems with this fantasy were quickly apparent: A) gets crowded up at the masthead and down at the stemhead B) bending the masthead - wouldn't damage the mast, but would screw up the sail shape enough to lose any of the advantages of this rig. C) COST! Holy cow, my sailmaker quoted me a price nearly as much as my jib and main combined! Ripstop Nylon is EXPENSIVE, and anything else will soon be blown out. Not to mention a new halyard block, stem downhaul rig, turning blocks, cleats, etc.
Hence my TLDR conclusion - *IF* I was actually cruising the boat, where I might spend all day or a few days in very light air, then sure, might be worth it. If it's just my usual knocking about on the lake and the wind dies down, I just can't see the value of ghosting home at 2.5 knots instead of 1 knot. Ghosting is ghosting, and I DO enjoy the mental challenge of it. But if I'm in a hurry to get home, I'll just fire up the engine.
As it turns out, these drifting sails are indeed mostly marketed to long distance cruisers (where an extra knot makes one hell of a difference!) rather than daysailers of any ilk. Racers are another story, depending on the class and race they are limited not only on what sails they can carry but also how MANY sails they can carry. Mini-Transats, for instance, are only allowed 7, of which one is the storm-job, so really only 6 (including the main). So one can see how a "multi-talented" Code-something hybrid foresail becomes very attractive. But for "round-the -buoys" beer-can sailing? Notsomuch, unless you are sailing with full crew, unlimited money, and the rulebook permits. And even then, not much of a difference, after all EVERYONE will be sailing the Code-Whatever, so what's the point?
Anyway, I don't mean to rain on your Drifter Parade, just sharing my thoughts on the whole subject. And who doesn't love a good "Whomper?" Put up the Whomper!
![Wink ;-)](./images/smilies/icon_wink.gif)