UNIX for Dummies Questions & Answers

hello everyone. i am working on getting my network+ and server+ certs. after that i want to get a unix cert, but i don't know what's the most needed. i've checked the web sites for sun, ibm, and hp and they all claim to have the fastest, most stable, open source compatible unix system that sets all kinds of bech marks. i've asked some of my IT friends what servers they see a lot and it seems like they see all of them with HP 1st, IBM 2nd and Sun 3rd. but that's just them. i assume some would see Sun more or IBM. is there anywhere i can look to see what's officially the most popular commercial unix?

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