Good points for sure John. I was not overly concerned about the weight difference. I climb 5% plenty, and even with my cargo bike that weighs a ton, it's no sweat.
But now we hear there is a much steeper hill involved, 14% ! Yeah, now the weight really matters. That is an order of magnitude steeper.
More data please. This hill is 500 feet long, or 500 feet tall?
I think you will still make it, but your motor will get toasty hot doing it. You will have to pedal your guts out for that 500 ft in a low gear. I highly recomend you install a thermometer inside the motor. This will help you determine how you can climb the hill coolest. Chances are, charge it WOT will be best. But it could be better to actually back off the throttle near the top, and use the motor to assist you to climb the hill much slower. The idea is, if your motor is only going to be able to use 500w, don't give it 2000 so it can make heat with it. The further you make it up the hill on momentum the better, so a 48v battery will help. You can start up the hill at 4 mph faster with 48v.
The rest of your ride, with no more than 5% grades, should be no particular problem with the Hs or the Ht motor. I don't advocate climing the hills no pedaling, but you should be able to climb 5%, and still not pop huge sweat, or breathe too hard to talk. Just a nice moderate effort to help the motor keep it's cool.
As others will tell you, you can get stuff with zero customer support cheaper. But Grin is still the best vendor in the world. Not the cheapest, just the best. Justin does more R&D than anybody, including little tests like riding across entire continents.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.