Roger Long wrote:

If you want to charge your batteries faster and harder than they should be
charged, are willing to put up with crawling around on top of them sucking
acid out of them with a hydrometer and putting distilled water back in to
them to repair the damage you have done to them, and are willing to accept
the small but quite real danger of having carrying free acid around in your
boat, wet cells will give you more bang for the buck and faster charging.

If you can live with charging at reasonable charging rates, you'll have a
safer boat and get better performance with AGM's. Remember, the outfit that
made such a strong recommendation to me about AGM's builds many unattended
mission critical systems. That's a good description of how I would like my
battery bank to be. There are a lot of mechanical things I like fiddling
with on a boat but batteries are not one of them.

You are not correctly stating the case by using the phrases 'faster and
harder than they should be charged' and 'reasonable charging rates'.
But it all depends on your use. If you use a main engine or a generator
to charge then I think AGM or gel are out of the question. Unattended
operation may require specific requirements. But these are not
requirements for boat use. As you say, there are many mechanical (and
other) things on a boat to fiddle with, and I don't understand the logic
that batteries should not be one of them. You mention using a
hydrometer, the only way to find the real state of charge for a
lead-acid battery. What is the alternative procedure for AGM? There is
none: there simply is no way to find the real state of charge of an AGM!
I would say that simply rules them out for anything mission-cricial. Yes
it may not be fun but batteries SHOULD be one of the things to 'fiddle'
with, IMHO.
If you read the article then you will also have read that if you are
willing to use 'reasonable charging rates' (=slow charging), standard
lead-acid is 'maintenance free' just like AGM and gel.
But AGM and gel are much more expensive.
You definitely seem to be wrong when you say that AGM will give you
better performance - even when using 'reasonable' charging rates. From
what I read they will NEVER do that and will most likely fare a lot
worse than standard lead-acid, for ANY application.

So to quote the article, AGM is good if you want to put your boat upside
down for an hour or two. In all other cases, use standard lead-acid.