Parallel then series, or the other way around?

I bought four 6V AGMs. Evidently I'll be doing parallel + series to get to 12V, but I'm wondering if it makes any practical difference whether I wire each pair in series (to get a pair of 12V batteries, effectively) - and then wire those in parallel, or whether I should wire each pair in parallel (giving 6V pairs) and then wire those in series?

I guess I'm wondering if it makes a difference in terms of balance, basically.

Is there an ideal wiring diagram out there? The batteries are the type with offset terminals (i.e., terminals are in diagonally opposite corners).