I did a lot of research on this subject prior to installing our new bank. One thing to think about is how the batteries will be used. John has a good write up on AGMs and full time cruising on his website Attainable Adventure Cruising
(I think you need to be a member now to see his ebook). AGMs need to regularly be fully charged which is almost impossible while living aboard at anchor. He warns, after finding out the hard way, that it will "ruin your batteries in a distressingly short time". His ebook is really informative if you are looking to go that way and may literally save you thousands of dollars by learning from his experience.
If you can regularly plug the charger into dock power then it shouldn't be a problem. In that case, AGMs are great and maintenance free. We didn't do anything with our batteries for the last 5 years and never had a problem.
But since we are going cruising, we decided to go with wet cells and chose Trojan T-105s, which have a good reputation and cost half as much as AGMs. That choice limited our placement to the cockpit locker because I couldn't find any other suitable spot for them. Plus, wet cells need regular checks/watering thus easily accessible.