Not sure what you are asking Billy. The heads at the TOP of the food chain haven't changed and likely won't. Not enough interest and or market. So whats there HAS been there for years and hasn't changed. There seems to be a variation every now and then, like this rumored 600-13X, but it's still in inline valve wedge head and as such will be limited and can't compete with other brands spread port head.

As for the heads towards the middle to bottom..........flip a coin. Not much difference in any of them.