Well, you need to define "best" as there are always tradeoffs.
There are many threads on this topic in the Forums. I'd strongly suggest that you read a few threads on this ... lots of info. available. But here's my short take on it all:
A marine battery is a reasonable compromise, but almost all marine batteries you'll find for sale in common places are dual purpose batteries ... they can be used for engine starting and then for relatively deep cycle use for powering 12v
"stuff" on the boat or rv. Golf cart batteries and true deep cycle batteries such as Lifelines are better at the deep cycle business and if properly cared for will last a lot longer in that sort of service, but not so good at engine starting, and indeed may not even have the sort of terminals that a starter motor application requires.
Second slice: sealed batteries such as Concord / Lifeline don't require attending to cell water level, because they're sealed, so they save some maintenance, and can be installed in places that are hard to get at ... while all "traditional" batteries tend to outgas some and need occasional water topping up if they are to live very long. But the sealed batteries are in the area of 2x cost to traditional ones.
Third slice: depends a lot upon what / how you charge them. If most of your charging is done by the converter that came with your coach, with some boost from your solar panel when you're "out there" then you'll likely want to stick with something like a traditonal / marine deep cycle battery, because the original converters tend to cook batteries to death by overcharging them and will quickly ruin sealed cells. (Even so, most of the remedy is not to charge more than you need and to make sure your cells are topped up with fresh distilled water as needed).