Advantages and disadvantages of in-wheel motors and crankshaft drive motors in terms of weight
Alloy Wheel Hub Motor
Alloy Wheel Hub Motor makes the wheels heavier. The minimum extra weight is about five pounds, but it could be much more than that. This is part of the reason why the average weight of an e-bike is over 45 pounds.
Crankshaft drive motor
Mid-drive motors tend to be a lot lighter than hub drives. Both the engine and battery could be lighter. That said, they obviously do add weight to the bike.
Advantages and disadvantages of in-wheel motor and crankshaft drive motor in terms of power
In-wheel motor
In-wheel motors work fairly simply, so they are very powerful. In most countries, the only limit is how much power you are legally allowed to have on your bike. This means you can ride great distances, drive extremely fast and navigate huge hills. All with minimal pedaling, if you like.
Crankshaft drive motor
The main limitation of crank drive motors is that they are limited by the strength of the chain and sprocket. Almost all systems to date have used standard bicycle chains and sprockets, which have never been designed for motorized use, so power must be kept fairly low. In practice, these motors are usually limited to 250 W.
This is of course balanced in part by the fact that the mid-drive motor works in tandem with your gears.
The bottom line on power, though, is that if power is the most important thing to you, you'll probably prefer a hub-drive motor.