If I had lied and told you that he had a 100GB drive would you have said anything?
They are the same in the sense that they have the same capabilities and are both compatible with OS X. However, my LG external burner is the same (with regards to capabilities) as the LiteOn burner in Tyranicus' Hackintosh, and yet they are different manufacturers.
My Mac shipped with 2*256MB Hynix RAM, my buddy's MacBook with 2*256 of Samsung, there, now are you happy with the comparison and the point that a manufacturer is idiotic unless they get multiple vendors?
How else do you think it is that Intel and AMD really go too majorly at odds (that I have heard of) with each other? IBM required Intel to give their designs to AMD or they wouldn't do business with either of them. IBM required having at least 2 sources of parts for all their computers.
You got a different brand of drive, you will notice next to no difference, and if it should fail, you might get a different brand as the replacement. OS X being the closed environment that it is, you can be sure that this new drive will work just as well as the old one.