I have an Odyssey battery, and I love it. I bought it specifically because it is completely sealed and doesn't need to be vented, so I could squeeze it into a corner under the gaucho.
I bought it from a local family-owned RV shop and they said they had tried them out in their own RVs and boats, and were really happy with them. I decided to splurge on it since it was the last piece of the big restoration a couple years ago, and it was the only battery I could find that was truly completely sealed, which was important since it was going to be under the head of the bed. It did cost about $200.
See, nothing's too expensive to be found in an Airstream...