I’ve installed a handful of systems where the DVD player is mounted on the floor, and a couple dozen of the overhead ones. I work at a car stereo/video/alarm/sunroof/leather shop, but mainly doing alarms and remote starts. Still, I can tell you what I know of the video systems.
-I’ve never heard of a customer comeback from a noisy DVD transport with either system. And I’ve never heard noise myself. (For the overhead consoles, we’re using the 7" Audiovox VOD705DL and the 8" VOD805DL.)
-The all-in-one overhead unit costs more for us to buy than separate pieces, but requires less labor. As you see, customer cost turns out around the same.
-You may, now or in the future, consider hooking up your Playstation or other video game console into the car on long trips. If you have an all-in-one, this will mean audio/video cables hanging from the roof down to the game console. An under-seat DVD player, with front-panel inputs, would be a little neater.
-In either case, most of the DVD player’s functions can be accessed by remote, with a nice on-screen display. Still, wading through luggage and food wrappers to push buttons and swap discs on a floor-mounted player isn’t much fun.
-The all-in-ones are thicker, even when folded up. It may block the view from your rear-view mirror---- maybe the shop will let you sit in the driver’s seat of another customer’s car to see if it’ll be a problem.
----With either system, a sort of mounting ring may be used, which makes the device thicker yet. Whether or not the ring is needed, depends on how much clearance there is inside your car’s ceiling, the installer’s skill level, and how much you’re willing to pay for the extra labor needed to flush-mount it without the ring.
-If you buy the system with separate pieces, and one of them should break after warranty, you’ll only have to pay to replace that one piece-----if any part of the all-in-one breaks, you’ll be replacing everything.
-If the DVD player is mounted under one of the rear seats of a van or SUV, you’ll have trouble using the vehicle to haul lumber or other large objects—see if the installer can get it under the front passenger seat instead. Or they can attach it to the floor with Velrco instead of screws—you could remove and unplug it when necessary.
So I guess I can’t make your decision for you, but at least there are some more points for you to consider.