If you want to be reasonably certain that something works with a recent version of Windows, look for the "Logo Certified" designation on the product/box and see if the product is listed in the Hardware
Compatibility List (HCL) on the Microsoft web sites. The HCL has some fancy new name...Windows Catalog or something like that for the newer OSes.
In order for a product to be listed, it has to pass extensive real-world tests, so you can be reasonably certain it works. No listing doesn't mean it won't work--it just means either someone couldn't afford the testing, or
couldn't pass it, or didn't care about it.
On the serial DB9 ports you are concerned usually with pins 2 and 3, which are the TX and RX pins, and pin 5 is usually a data ground line. A lot of documentation
can be confusing because the "TX" from one device connects to the "RX" on another, and vice versa. So as you look at a connection...if one pin is TX on your GPS, the corresponding wire on a cable is the "RX" connection on whatever it goes to. Bottom line is that if something doesn't work, 2/3 are usually reversed, or the data rate and parity aren't set right. The devices are robust enough that reversing 2/3 won't hurt anything, it just won't work till you swap 'em back again.
differences often reflect what the market can bear, or the release of new chipsets, or something going from "made by hand in Switzerland" to "banged out in China".