Endless topic indeed. Given what and how hasbeen presented by the OP.
IMO, some read/research is in order before asking for advice and following it blindly.
You wanted something "with more capacity and/or that will hold the charge longer", because your original batts don't hold the charge well after 5-6 years. A few points to consider:
1) 2*6V at 225 AH each will not give you "more capacity" than 2*12V 112 AH each. Choosing 2*6V for this reason alone would be a big mistake. I'm not saying that choosing 2*6V would be a mistake in general.
2) AGM batteries 95 AH at $190 are about as cheap as you can get. Possibly, a lower quality brand. Decent 100 AH AGM would cost a little more (not much more, though). Buying AGM other than a reputable brand would be a waste of money.
3) 105 AH $100 wet deep cycle battery is clearly in the category "too good to be true".
4) I sense a lack of proper maintenance on those old 2*12V that are dying or not holding charge well. Without proper charging and maintenance you're going to kill any battery in under 6 years, no matter how good. Though, as others noted, your old batts were not deep cycle, which surely contributed to their early demise. Still, any battery you need to treat right.
