Advantages and disadvantages of Wheel Hub Motor and crankshaft drive motor in installation
Anyone handy can buy an e-bike kit with a hub motor and install it on a bike they already own. From personal experience, pretty much any bike shop can do it. You don't need someone specializing in e-bikes.
In-wheel motors are relatively simple motors and are completely self-contained. This means you can use an off-the-shelf bike on just about any bike, and if you upgrade your bike, you can move it from bike to bike.
Crankshaft drive motor
Installing a crank drive motor is highly technical, and very few people can buy one and install it on their existing bike. Most commonly, the crank drive motor is part of the original manufacture of the e-bike.
Advantages and disadvantages of in-wheel motors and crankshaft drive motors in terms of ride feel
In-wheel motors and mid-drive motors
The hub motor basically pushes you from behind through your rear wheel. In contrast, the crank motor is almost integrated with your pedals. Because of this, many experienced cyclists say that an e-bike with a crankshaft-driven motor provides a more natural riding feel.
On the other hand, if your main concern is traffic, then feeling may not be your primary concern.
Advantages and disadvantages of in-wheel motors and crankshaft drive motors in engine heating
The hub motor is completely sealed. This means that there could theoretically be an overheating problem, as there is no easy way for the heat to escape. However, most units have controllers that monitor and control this. A quality bike from a reputable manufacturer shouldn't have problems with overheating. I have never had an overheating problem in the years of using hub motors.
Crank drive motors typically have a scalloped housing that dissipates heat more efficiently than hub motors.