S4: Elite Lithium X.0 vs 72v

[Inscrutable]

Looking at a new cart, and a little confused by all the concerned threads re range and speed. We probably only go 15mi or so on flat land between charges, and 20mph is fine.
Any recommendations whether to go 2.0 or 3.0 or 4.0 (knowing it’s $1000 for each step up)?
And am I just as well served going 72v lead-acid and saving the $$ ?

(And if this isn’t heresy here, we also have looked at Onward, but just about as confusing, and haven’t found comparison thread(s) here yet)

Thanks!