AGM's have one asspect missed. It takes less input to charge them. They do have tighter regulation requirements but them a good regualtor is required for any serious use no matter what you use. If you swap an AGM for a flood and don't change the regualtor then you are screwed. They don't swap out without changing the regulation settings. That is why they often get a bad rap that is undeserved.
I had 3 banks using 6 Trojan 6 Volt golf carts. They lasted a long time and do work well and are cheap. They also out gas and 4 were destryoying my AC heat exchanger and 2 were under the main electrical panel. The out gas eats aluminum and most other metals.
Flood batteries need venting and can't hanlde heeling well at all. You have to watch them for low water and one bad cell trashes the whole bank - hence my having had three banks. You can't group them more than 2 per bank and be safe. I now have one starting battery and one bank of 2 Lifeline AGM 4D's. Cost is higher but it's a simpler, easier to use, with more power and less weight that recharge faster with no maintence. The cost was about $100 more. I was able to reset all my regulation and charging systems for AGM from Flood. I'm starting my third season and so far they are fine.
A link 10 batter=y monitor is a great thing to have for any type of bank. It really helps you know how you really use your power and you are alrted to trouble when you discharge too low.