I would compare their features on a site like Newegg.com to see if the one you got is missing something you want. They are close in price--the MSI is about $5 more than the ASRock at Newegg. I personally prefer the MSI brand, but they are probably comparable.
I'd also ask your builder why they didn't comply with what you ordered. Maybe they'll offer a little rebate vs. you returning it.