The most important thing for long rides is the charging speed. The capacity of the additional PowerTank can be used once a day, while recharging lets you use the same capacity multiple times a day.
Lenny, the power tank is good only once a day??? Explain how that works. If you charge up a 13kw battery you go X number of miles, if you charge up a 16.3kw battery you go Y number of miles. Every time you recharge you can either go X or Y miles. Why would you choose X because Y "can only be used once a day"?
Heres a simple example.
Take your two bikes, Bob buys the 13kw bike with a fast charger and Tim buys the 16.3kw bike with the stock charger.
They both get excited with their new bikes and run them down to near 0%.
Bob goes only 80 miles before having to plug in.
Tim gets to go 100 miles before also plugging in.
Bob waits between 40mins and 3 hours (depending on which fast charger he has) and is at 85-100%... he goes off and rides another 50 to 80 miles.
Tim waits at home for 3 hours. his bike is 37% charged.
Bob then plugs in again, charges in another 40min to 3h and goes and rides another 50-80mi
Tim has been waiting 6hours to ride. his bike is 75% charged.
Bob plugs in again, and about an hour later Tim asks him to go riding.
Even though bob has already ridden 240+ high speed miles today, Bob is partially charged(or full, depending on charger) and can go meet Tim.
They both can ride again, and the cycle repeats.
Now, if Tim was at work or sleeping for those 8 hours... its no big deal.
If Tim was on a road trip, and is spending this sitting around in the middle of nowhere waiting, it sucks.
For my day to day usage... it doesnt matter, I plug in when im not riding.
For weekend fun, I might want to do 600 miles that day. I want to recharge fast.
So while the ideal is a large battery and a fast charger, the OEM tanks occupy the same space.
Also, the power tank is heavy.... the bike feels better without it. However that's a different, even more subjective discussion.