I just refuse to spend the extra money because I am not convinced it is really any better than any other half decent battery out there.
And there is nothing wrong with that, it is a personal choice. But the benefits to an AGM (Absorbed Glass Mat) Battery is that they are much more stable, they are sealed, you do not have to add distilled water annually, and they just flat out last longer. A lot of people do not know what it means to properly maintain a battery, there is more to it than cleaning the terminals when they stop working.
There are other benefits to AGM batteries, like the fact that they last well over twice as long as a Lead acid battery. most reputable lead acid batteries are rated for 4-5 years, while most AGM batteries are rated for 8-10 years. The construction makes it nearly impossible for the plates to short out, because there is a non conductive mat in between the circular "plates" as opposed to flat open "flooded" plates that get corroded or warp when fully discharged causing dead cells.
So basically Double the price double the life. Some may say it is 6 in one half dozen the other, but I lean toward the non maintenance battery myself.