Mostly it comes down to drivers, but in OS X I don't really know, since most of the drivers are modifications of other drivers...
In Windows Intel has lower CPU overheads and some advanced driver settings.
That said, a lot of Intel's "consumer" NICs have lacked things like Jumbo Packets which is meant to improve the transfer of large chunks of data if the network switch supports it, something that's still rare on most home routers for example.
Realtek doesn't have the best reputation, but in all honesty, they're not that much worse than anyone else these days.
Most of Intel's advantages these days are in software features of which many don't apply for home users.
looking forward to getting this board
