Not a lot of responses to this. I am not one to spend a lot of time thinking about batteries. I went to Sam's Club and got their AGM deep cycles a couple of years ago and they seem to be doing fine. I don't like to mess with flooded cells so they don't come onto my radar screen.
If you can handle the minimal maintenance requirements of FLA you cannot find a better value than the 6V GC2s from Sam's Club or Batteries Plus, ~ $90 each. Mine are on their 4th year and still hold 6.3V and 1.275 specific gravity.