If the part sells, they'll stock it, i.e. "support it"

Next question. What makes parts sell? Field population.

Buy a brand with lots of population in the field (more importantly your field, your country) and there will be plenty of OEM support and an active aftermarket as well.

Buy a brand that is rarely seen in your neck of the woods...you're asking for trouble down the line.

Need an app for iphone? There's probably one out there. Need an app for Windows CE mobile? Good luck.