W/o exact measurements i would say that based on my own exp. it is easier to shed some weight -7-10lb (either from bike, faster /lighter tires /bodyweighy )is ideal and that would equalize the 400wh battery with the benefits of the 500wh bat. W/o inccuring the additional cost . In a few years a 900wh , 1kw battery would be common place.
Ex. In 2015 the brand i have (easy motion )!had a 416wh batteries , in 2019 some of their bikes have now a 750wh battery.