My two cents,
I've seen the Pro9 and I've seen the K1 from Honigs. Here's the difference I've seen. The Pro9 has plastic plates inside of the foam which takes a pretty decent shot with out harm. The Honigs has the plates in front of the foam which deaden the blow a lot more which gives you more protection. The major difference is the price. You pay more for the plates to be in front of the foam. Another comparable CP to the Honigs with plates in front of foam is the All-Star Pro Level CP. It's more than the Pro9 but cheaper that the K1. I'm in the process of choosing a new CP my self and have the K1, All-Star & Pro9 in my sights. I have been doing Travel ball all the way up to 18U and had been wearing the Wilson Gary Davis CP but have felt the shots in the upper divisions (16U & up) more lately. All three choices have the thick foam padding, just the plastic plate placements are different. The All-Star seems to conform to my well rounded body more.