In my experience and others I know, AGM is a much safer battery with regard to leakage as compared to wet cell, but as to longevity, AGM shows no advantage to me.
What works for me is keeping a decent charge maintained on either type battery. I have a couple of small smart chargers that I rotate around every few days that keeps them charged, and allows a little rest period. With deltran pigtails installed, it's a breeze.
Many look for the best deal, but I also want ease of replacement in the event of a warranty issue. The wife's car battery went out 6 months into a 4 year warranty earlier this year, nice that the store was less than 10 miles from the house, and they had it in stock. Doesn't happen often, but it sure can!