Most manufactured bikes with integrated batteries look much better than kits, because cable routing and battery sits nicely within the frame.
The problem comes when the controller or the battery needs replacing after a few years and when you try to buy one or the other you can find they are obsolete.
The e-bike market is progressive and the bikes you buy today won’t be available in a couple of years time and you can have trouble sourcing these items.
Another thing to consider is your riding style and whether a hub or mid drive motor is best for your needs.
For example, if you are an aggressive off road rider then a mid motor is preferable over a hub motor.
Owners are usually locked out of the display on manufactured e-bikes so you are limited to what parameters you can change on the display. This includes the mileage, so those two bikes are probably genuine miles.
Some people prefer kits over prebuilt bikes for several reasons.
1. They like their existing bike but want to add a motor.
2. Obsolescence is not so much of a problem with the battery, controller, display or motor.
3. Displays for kits aren’t locked, so the controller is configurable.
4. Many owners although they don’t want to publicly admit it, want more power than is legally available from a manufactured bike, so build from separate parts or from a kit that is capable of much more power.
7 years is a long time in the e-bike world. Batteries will definitely improve during that period and will become cheaper with more range. And today’s batteries are unlikely to still be working at good capacity in 7 years time if used regularly because they will run out of charge cycles.
There are a few things to be mindful about motors.
1. They aren’t particularly waterproof, so if you are constantly wading through rivers they will get water inside which will start rusting the internals.
2. Bearings will wear out after high mileages, but these can be replaced.
3. If you hot rod your motor by running it at a high power than it is rated for, then it can overheat and cause magnet damage, burn out the windings and melt plastic gears.