Mid drives seem to be choice for hill climbing ability; but, very few have throttles. Most mid drives start where rear hub ebikes end for bike prices. Your best bet might be aftermarket/custom build.
Mid drives mid drives mid drives mid drives. People on this website have mid-drives stuck in their mind like glue. Extremely important, bike shops make more profit on mid-drives so those are obviously superior.
I use hub drives on 15% grades all the time. Mid drive maintenance and part unavailability problems (after a few years) (don't believe me read the article mikedd wrote about the incompatibility of the modern bosch mid drives with the bike frames that the original bosch drives were installed in) are required in
EUROPE where ebikes are limited by law to 350 W. Europe also has 20 mile grades where heat buildup is a problem. The O.P. lives in NY state with roller grades. He can legally buy a 1000 w (26 A) hub drive.
From the picture found by bing, it appears rad bikes, at least the radrover shown me, is a DD hub motor. Those are cheap and not entirely suitable to hills. But, I've been using one at 330 lb gross weight for 8 months on 15% grades. The secret is, run the speed up with the throttle as fast as practicle before the grade, to get the motor up into its proper operating speed. Then run full throttle up the grade. DD hub drives are not very efficient on steep grades, and I've been running a 17 AH battery down from 50 v to 43 v in 30 miles with 8 of them being very hilly.
I last month managed to get my 1000 W
geared hub drive installed and compatible with the throttle only controller that came with the DD hub. Top speed is lower, but the battery draw on my last trip (including a stiff headwind) was 50 v to 48 v. So the geared hub drive is much more efficient on steep hills. Duh, read
Audel's Motor Book for the reasons. I don't need the 25 mph top speed of the DD drive.
In NY state borsht belt, I imagine what steep hills that exist are rollers like we have here. Ie, short upgrades followed by short downgrades. This doesn't overheat the motor even using full throttle. I've had California obsessed vendors refuse to sell me a geared hub drive because of my "excessive" 330 lb gross weight. (I carry supplies to my summer camp). Those coastal people have 20 mile grades that people ride all the time, and probably burn out motors frequently. The Appalachians are
NOT the Sierra Madres or Rockies. Note I pedal downhill with no power; there are deer here and I can stop faster uphill than down.
So if GPmike really does burn out a DD motor on his rad, just buy a geared hub drive. It should bolt right in. they are all 135 mm dropouts. A little fooling with the wire harness, the original controller might work. Since new controllers are $35, I'd say buy a new one with the motor along with throttle, but you may not have to install it.