The biggest advantages of hubbies is the same as for ebikes, they're easier and it saves space (the biggest premium on ebikes since batteries use so much space.
Power is equal to rpm X torque. That means for a given power a motor can be smaller by running higher rpm, which means a gear reduction.
You said "lightweight motorcycle", but that's a bit vague. For the accurate advice about the choice, you really need to specifically define how it will be used, ie speed, range, terrain, etc. Continuous speed and range are the killer for an electric anything, because what you give up to wind in the form of aero drag eats battery capacity so they increase pack size, weight and cost. In terms of terrain, hubbies are best suited for street use with flat terrain. While little guys get away with slapping a hubbie on a mountain bike and taking it off road, as you get more like a motorcycle in terms of weight, load, and performance expectations a hubbie will be an overheating anchor of unsprung weight in the wheel if you head off road on all but the simplest trail riding. 2 wheel drive with dual hubbies might be an exception, but I've yet to build one to confirm their capability.
Last there's the biggest factor that amazingly people still don't get, and it ties in with power = rpm X torque. The smaller the wheel diameter, the more performance you can get out of ANY good DD hubmotor. It's straight forward physics. The primary limitation of all hubmotors is heat, which comes from 2 sources, iron losses and copper losses. Iron losses increase mostly linear with rpm, but copper losses increase with the square of current while torque only increases linearly with current. While this is a bit oversimplified, I can't stress enough the importance of understanding this general concept. It's what enables me, a fat guy, to enjoy the highest performance from hubmotors on this forum for the past decade.
While the out-of-production high efficiency hubbies I've used since 2012 are part of the story, the real reason enabling my higher performance is that I run as small a wheel as possible. eg On the tiny scooter I use for my current 40 mile roundtrip commute, I fit the smallest 10" scooter tire I could find, which has a 16.5" OD inflated. The mid size motor I use has a Kv of 14.3rpm/volt (torque constant .68Nm/A) powered with a 111V nominal pack, and it comes in at about 14kg with the tire and built on rim. It sucks a peak of 150A from the battery through the 2 controllers (75A/ea) required to run it, for almost 18kw input with a fresh charge even after voltage sag. Gear that kind of torque and power with a small tire for a top speed just above 70mph and I slaughter everything I run across at every stoplight every day. My almost 3kwh pack gives me 40-50 miles of fun performance riding (probably double that range on flat land going slow) with the only real compromises being that it's a bit small and uncomfortable and it's only nice on smoother roads.
Despite my love of the silence, simplicity, and efficiency of my hubbies, when I do build an offroad bike, the motor will be out of the wheel.