Heads question

Thanks. Kinda what I thought, too, but some folks on the sight act as if the X heads are the Holy Grail. I wasn't sure if there were any casting differences besides the valves.
Plus, if I put the X heads on, I'd be back to 13:1 compression, which is over the top for pump gas and composite head gaskets (I'd need o-rings for sure). I was just curious about the castings themselves, and whether my engine guy was just assuming the valve size would make no difference.