Cl70
SLA batteries in this size 6V will be about $30 which is twice the money. Just get the cheapy and you'll be fine. I have an AWESOME battery tender/ reconditioning device that I'm about to write a review on here. It's amazing how long batteries will last with a tender on them - although the Battery Tender CAN overcharge a motorcycle size battery after 3 mos of use on one. So you don't want to have them connected ALL the time.
The new charger I have WON'T overcook the battery and it does 6 and 12V which is unheard of in a battery tender type low amp charger. Just gimme a day or two to get my review and pictures done here. And yeah just get the cheapy battery in my opinion - and invest a little cash in a tender to keep all your batteries in good shape. That will save you more money in the long run. But if I can find a decent SLA I'll report back. I might get a reseller account opened up at Batteries Plus which will knock the price down on all batteries - and they have am all!