Showerguard is a product made by Guardian that is actually in the glass as the glass is manufactured and carries a lifetime warranty. Cardinal 10 is an aftermarket product that is applied at the shower manufacturers facility and carries a 10 year warranty. The price difference is generally about 50% more for the showerguard and while it is universally known as a better product the decision is your as to wether or not you spend the extra money. A coating is in my opinion is definitely a good choice just up to you which to go with. I happen to work for a architectural glass and aluminum company and sell both as well as Diamon Fusion just so everyone knows my angle and am not spam!

Thank you so much for your very helpful information, millworkman.

For us that had to battle two existing showers,my partner and I found a very simple DIY project that solved our problems. We applied a kit from Crystal Clear Shower Glass Enhancement we found on Amazon. The kit comes complete with every thing needed to restore shower glass, seal and protect the clean glass from hard water staining and scum buildup. I still squeegee but with very little effort. The shower glass is no longer a problem and it has lasted well over a year!

@millworkman - Do you recommend Cardinal 10 or Diamond Fusion?