They show up on eBay.
I'd probably leave them off since they detract from the clean look of the car.
Once you install them, you pretty much have to leave them on there for the life of the paint job since they are likely to do some damage when installed.
If you DO end up chipping your door edges by slamming your doors into parked cars
then you can install them to hide the damage! ... but I'll bet you'll be careful.