The other 500 watt motor is rear hub, internally geared. (not direct drive like the Rad). The torque rating on the other motor is 65 nm. If Rad would publish their torque rating or simply provide it to the customer, then we'd have an idea if it was just a weaker motor, or if there is some other issue.
My own experience with direct drives, even if they are higher watt ratings like this 750, is similar to what AHicks describes in his post above. They are typically slow to accelerate, and when you get on a hill, if you dont have a lot of momentum (speed) going into the hill, it will bog down, and not provide anywhere near the assistance you would feel when the road is flat. Some older folks just don't ride that fast, and so the slower the pace they have, will put them in more strain when going up hills. Another way to get around that lack of acceleration with direct drives, is to allow a larger current inrush, but that would mean you need a larger controller (high amp rating), but then you'd suck the battery dry in a heartbeat. (the battery BMS would have to be designed to allow that higher current inrush too, so its not a simple component change to accomplish this.) Hence why more ebikes OEM's, use IGH motors if they are providing a hub motor, than are using direct drive.
Usually if vendor is selling direct drive motors in kits, they are often sold with power ratings of 1000, 1500 watts, or even higher, but then you need a larger battery to get a decent range. They are also very inexpensive, so they are quite popular for DIY'rs. And since they are rather inexpensive it helps Rad keep their end price down, but still convey a seemingly higher wattage rating without disclosing the torque rating. For example, Prodecotech sells a 1200 watt direct drive motor, mounted in a 26" rim, with a controller, wiring harness and throttle (no pedal assist/no display) for $300. The direct drives can be very durable, but this sort of trade off, is what folks like this couple are probably experiencing. They said they wished they had a chance to test ride the Rad before buying.
It would be helpful to know the specs though, even if the torque rating is only applicable to a certain speed. I've seen 1500 watt direct drive motors, have torque ratings as low as 35 nm. I've seen 750 watt direct drive motors at only 25 nm. So I suspect the Rad is somewhere between 25 nm and 35 nm, which is a torque level you can get out of a 250 watt geared hub motor.
In otherwords, torque rating tells you a lot more about the amount of actual power delivered, and high climbing ability, than does watt rating. (most forum members know this now, as mid drives rated at 250 watts, appropriately geared, can easily deliver up to 65nm or even higher).
Maybe someone out there has done a bench test on this Rad 750 w motor ? I know there are people who can do this, and provide some data.
