Matt, the only advantage I've been able to see is the Optima (and competing
brands) are sealed, keeping gases from the battery out of the interior of
the van.  To me this is only a concern if I run the battery flat and use a
hot, fast charger.  If I lived in the van full time al la Roadhaus, I'd
probably go that route.  But when I replaced my aux battery last summer I
went with a cheap lead-acid battery.  Even if I cycle it to deep and shorten
it's life I can replace it three times before it adds up to one Optima.