This particular web site doesn't attract many recumbent or ebike friendly people. Bent riders on line has a "Power Assist" forum, have to wonder if you will get a better response there.
As for your battery question both of those units are pretty good sized. But in the end the answer comes down to cost, weight and the space you have to mount the unit. To me bigger batteries means you won't need to charge it as often, and since batteries are rated in charge cycles my simple mind thinks this will increase the time between battery replacements.