Two big batteries, or three small batteries

This applies to all equipment, just not trucks, but I asked here.

for some reason, I seem to have better luck with just two big batteries, as three small ones, even though the CCa adds up around to the same # or even more with the small batteries. Just wondering what everyone else thinks.

And is it just me or are batteries not getting any better. I used to figure 5-7 years, now I feel lucky in the 3-5 year.

Two big batteries, or three small batteries