Endurance Formula performs more in line with traditional in-market sealant. According to the Orange Seal website, it effectively patches holes half the size as the original formula, but lasts over twice as long before drying out in your tire. I rode for over 50,000 miles on the Endurance formula before I finally had my first full flat, and it will be the end of the Endurance formula for me. The reason being - with the Original formula, not only did it seal everything - but it sealed a sidewall puncture on a gravel descent, and I was able to carefully ride the bike home with it, with no loss of air. There is a compromise when going to the Endurance formula. Both are great - but the description of "up to 1/4 of an inch" is actually misleading. The original claims for this were for 1/8th inch hole, which is more than adequate for most punctures. Just be sure to select the appropriate formula for your needs - there is no "one size fits all".
I had a leak in my rear tire that the sealant took far too long to seal. Seemed like a pretty ordinary puncture that it just didn't want to seal. It did do a good job of putting a coat on my down tube. My eventual solution once I noted the tire was near flat was to rotate the tire to the six o'clock position, agitate, and wait. After some time I added air with a CO2 cartridge and went on. After another 20 miles I had to inflate again but at last when I got home it sealed.
Not much you can say that hasn't been said about the best tire sealant available. I've found that OrangeSeal works better than other brands for road tires. Still not always perfect seals, sometimes it takes adding some extra air or a plug but it is still superior.