Just like everything in the esmoking world it's going to come down to WHAT ARE YOU LOOKING FOR IN YOUR VAPING EXPERIENCE.
No one can definitively tell you that x juice is better than y, mod a is better than mod b, 3.7v is better than 6v.
My experience with the higher voltage. Yes the hit is stronger the volume of the vapor is larger but it uses a lot of juice and requires you to be more vigilant in determining the state of your atomizer, i.e., is it too dry, is it too hot etc. So there is a learning curve.
If you're happy with the way your e-cig is working using the lower voltage batteries but are wanting longer battery life and cheaper batteries, stick with the mods that use the 3.7 range voltage.
Again, my two cents ( and I'm running out of pennies)