I suppose there are other good greases, but the stuff Wilson Combat developed (Ultamalube) is tough to beat. After watching the 1/2 hour video of it's development & testing, you'd be sold too. They put the stuff head to head with a number of other super lubes and there just plain wasn't any comparison. It's been about 5 years since I watched that video, but they were doing some pretty heavy duty testing, stuff that literally destroyed heavy metal test bars "protected" by the other products, & only minor (if any) wear was imposed upon the bars treated with their product. It took about 10,000 rounds through my new P239 before the finish on the rails even began to show slight signs of wear, & after 40,000 rounds it aint much worse.
Ok, I just pulled the slide off, afraid that someone would want a picture to back up my story. Guess what? Aint no wear, period. There is no bare metal showing on the slide rails at all. There is a tiny spot at each end that is starting to look dark brown instead of black. I have dry practiced with this gun (including a LOT of malfunction clearance drills) a lot more then I have shot it. Oh, and I typically run 600-1,500 rounds through it in a weekend without cleaning it til the fun is over. I bought 3 tubes, gave one to a buddy, one is still unopened, and the 3rd is still at least 3/4 full after using it on all of my rifles & pistols for the last 5 years. And no, I don't own any other Wilson Combat products, am not an employee or stockholder, & don't get kickbacks. Ultamalube is just great stuff!