Which Is Better 6v or 12v

This is a personal preference, but I would recommend the 12V batteries.

The 12V batteries will give you more amp-hours, which means they can last more hours before needing to be recharged.

I would recommend two 12V batteries if you are looking for high amperage and long lasting batteries.

If you are looking for cheaper batteries, I would recommend 6V batteries because they have lower amperage.