Nothing affects the way a board rides more than the drive system. This plays into the acceleration you get, energy efficiency, ride quality, required maintenance, an perhaps most important, price. This post will break down all of your options and help you pick the best for you!
|Required Maintenance||Minimal||Lots||Slightly less than belt||Minimal|
|Ride||Bumpy||Great (depends on wheels)||Great (depends on wheels)||Great (depends on wheels)|
|Customization||None||Great (any wheels, variable ratio)||Good (any wheels)||Good (any wheels)|
|Noise||Very Quiet||Loud||Very loud||Slightly louder than hub|
|Ground Clearance||Perfect||Pretty good||Decent||Decent|
A hub motor drivetrain is when the motors are placed inside of the wheel. The urethane (wheel material) is glued to the motor housing. This is great because it saves space and reduces the number of moving parts resulting is lower maintenance costs. Energy usage is also lower because nothing is lost to friction. Hub motors also tend to be the cheapest option so if you're looking for a budget board, you might want to look here.
The downside of putting the motor inside of the wheel is that your motor needs to be smaller than the wheel. This results in reduced torque and acceleration. In addition, the center of the wheel is no longer soft so you're going to feel bumps more than a regular wheel. Some boards have started putting thicker urethane on the hubs which helps but doesn't fully solve the problem. Perhaps the biggest problem is that you can't change wheels, you're stuck with the stock setup.
Belt drive systems have great acceleration due to the available gearing in the belt/pulley system. They also allow to change wheels at any time assuming you have a compatible pulley for the wheel core. With this, you can get a really smooth ride by using soft wheels that eat bumps. Most systems also allow the rider to change the pulley ratios allowing you to adjust the torque/top speed balance. Another great quality of belt systems is their price. Being one of the most popular systems means that there's lots of competition and thus, a better price for us! The parts market is also very strong with lots of different pulley and belt options.
The biggest problem with belt drive in my opinion is the amount of required maintenance. You're going to need to replace the belts every couple hundred miles (depending on ride habits). It isn't hard to do but the costs and time do add up so you'll want to consider this when picking a drive system. Belt drive is also much louder than hub motors.
Gear drive gives you the acceleration and customization of a belt drive system but with less maintenance. These systems are still pretty new so there aren't many boards out yet that use them. I haven't been able to ride a gear drive system so I can't say too much about it but I think we're going to start seeing more of these in the near future :)
Some of the drawbacks of gear drive include the lower ground clearance, high pitched noise, and high cost.
Direct drive is the new kid on the block. We're just starting to see boards using this system and it's looking good so far. In this system, the motors are integrated into the hanger right in between the wheels and kingpin. You get a smooth ride, swappable wheels, and low maintenance requirements.
Since the motors are mounted right next to the wheels, you can't use a motor larger than your wheels. This also means that you don't have great ground clearance so avoid this system if riding on uneven terrain. Perhaps the biggest reason not to go with direct drive is the cost. As I said earlier, direct drive is very new which means there aren't many manufactures so the cost is still pretty high.