UPGP is the odd ball in the mix above, the rest are very similar styles of products in terms of how they atomize and cover the paint when you spray them on the surface, and how they leave the paint feeling. Opti-Seal, WG Liquid Seal, Blackfire Crystal Seal, these feel the most comparable in terms of properties, application, and performance. I prefer Liquid Seal and Crystal Seal over Opti-Seal because they`re scented, with LS having a cherry scent, and CS having a nice cotton candy type scent. All three of these really seem to spread nicely, level out well and wipe cleanly without much buffing with the microfiber.
McKee`s 37 10 Minute Paint Sealant feels a bit heavier in terms of application compared to the Opti-Seal trio above. Atomizes the same, takes just a bit more time to fully level but it does so easily with a final pass on a clean microfiber or after flipping the towel over to a clean section. Slightly more hydrophobic than the trio, unscented.
Meguiar`s Fast Finish is lighter than M37 10 Minute, I`d say on par with Opti-Seal in terms of wipe on/off, slightly more hydrophobic than the rest above, unscented. Fast Finish is an awesome choice if you really enjoy this style of sealant, I would say better durability than Opti-Seal. You probably won`t get as many uses out of the aerosol can though.
UPGP is the heaviest of the bunch, definitely needs a some additional wiping to get it to level out nicely, slickest feeling of the bunch. Can`t remember the exact hydrophobic performance off the top of my head but I believe it was stronger than Opti-Seal in the short term.
I`m actually a big fan of the Opti-Seal style sealants because they`re ridiculously easy to work with, but I will use them as toppers to a stronger base layer sealant. They aren`t going to quench the thirst of the fanatical hydrophobes like myself, but it`s always a pleasure to pull them out and enjoy the application process and end result.