There should be no difference at all between different client operating systems for EAP-TLS. Can you provide a bit more detail on what problems you are seeing?
Is the server certificate trusted by iOS? That's normally the reason these things fail. And in order to add a trusted CA certificate to an iPad, you need to use the iPhone Configuration Utility, or use Aruba's ClearPass OnBoard solution. It's not as easy with iOS as with Windows, MacOS, or even Android to add new trusted certificate authorities.
-Jon