MircoSD Class Differences...

Can anyone tell me what the differences are in say a normal Class 10 MicroSD card, and a Class 10 UHS-1 MicroSD card...? Is the UHS-1 version of the card usable in ANY device, or is it ONLY usable in UHS-1 specific devices... I'm so confused as to what is the right card to purchase for my Acekard 2i and for my Samsung Galaxy S2 Epic 4G Touch smartphone. These fucking card differences... why can't things just be simple... 
