You can't look at architecture in a vaccum. The integrated memory controller and other goodies on the phenom II is great, but would not have been realistic on older processes, because of the increase in thermals and die size it would create.
Phenom II is the newest, includes the largest instruction set, newer technologies, and the best process. It sits in the mid to mid-high end PC market.
Operon and Operon 64 are older, and are ran on older processes. As server chips, they were optimized for the best performance per watt, which they excelled at (on their process, which was BULK SOI at probabaly 90 or 130nm)
For their Time, the Operon's were a better chip, as they were competitive at the top end of the market, all the way down to the low end. Edit: of the server market.