6v or 12v?

I'd base my choice of batteries strictly on which one would allow me to stuff more AH's in the available space. There are more sizes of 12v batteries than just the group 27's you are comparing to. If you can fit 2 group 31's of the correct type, you could have more available AH's than the 2x6v.

:):)

6v for longer life and improved reliability.

I'd rather have (and do have) multiple 12v. If one is no good, you're still in business. And with the specs you mentioned, it's 220AH at 12v either way.

6v Because 110 AH is just that no mater how many batteries you have you still have 110 AH

6v
I had OEM 12v, went to solar and recommendations were all for 6v..

Something to do with Amps etc... no idea, and don't really care to get confused by it all.. but 6v was the recommended way.. longer lasting and deeper draw or something like that..

Downside is if one 6vt goes bad, you no long have a 12v system.. if I remember correctly... that was my main concern initially..

6V