It depends on whether it's important that I get a screen that works 100% the first time around. When I'm ordering for a client that's waiting on a repair, I use laptopscreen.com most of the time. Their service can't be beat and it's very rare that I get a bad screen. When it's something that I've gotten in on trade and I don't mind it sitting around for a few more days if I end up getting a bum screen, I buy the cheapest screen I can find used on eBay. Even buying used crap on eBay it's fine 90% of the time. It's also as much as 50% less than buying new from laptopscreen.com so it helps add to the bottom line.
We keep quite a few screens in stock (mostly ordered from laptopscreen.com) that we can use for a quick turnaround. There are only so many makes/models of screens. If we have to special order a screen, we typically buy 2 of them just so we have another one in stock. Then when we sell that one we buy 2 more. Some of these screens are virtually identical and will fit in many different models so we end up having a lot more than 1 or 2 on hand that will fit a lot of different laptops.
These are the factors used to determine whether a screen will work or not:
1. Screen size (duh)
2. Screen resolution
3. Screen aspect ratio (not such a big concern nowadays as 99% of screens are 16:9)
4. LDVS connection location (top left, top right, bottom left, bottom right, etc.)
5. Pin layout and # of pins
6. Backlight type
So long as the replacement screen and the original screen have all these things in common, it will work 99% of the time. The make/model of the screen is irrelevant. There are often both glossy and matte variations of the screens, but that's more of a personal preference and doesn't affect compatibility.