If you look at the whole set of issues facing a data center manager researching Solaris on SPARC versus AIX on Power in response to some senior executive with an IBM agenda the one thing that stands out is simply that most of the problems, including pricing, pertain to AIX and mainframe "headset" issues, not the Power architecture or IBM.
AIX 5L 5.3 is far behind - and the imitative Solaris 10 "features" in the current beta for 6L look more like complexity increasing paste ons than the kind of simplifying fundamental change characterizing Solaris 10. The Power6, on the other hand, is a pretty hot chip in its own right, a first step in a putative transition to Cell, and a credible test-by-customer for the higher gigahertz manufacturing processes needed for Cell.
Consider, however, Linux on Power: it isn't remotely in the "insanely great" category, but it works - and if Linux could eventually be tailored to Power the way Solaris is tailored to SPARC, the combination could work with IBM's business credibility to give Sun a real run for its customers.
Right now getting Linux code to run on Linux for PPC isn't very difficult - it's very inefficient, because of the endian change and the inappropriateness of the x86 specific ideas embedded in just about everything Linux, but it's relatively easy to do and it works. AIX code moves across to Linux fairly easily too - in part, I think, because the generational gap is much smaller than with Solaris: it's no coincidence that the Solaris to AIX porting materials on IBM's porting portal generally pertain Solaris 8 and earlier while the Linux to AIX stuff is reasonably current.
As a result there's an obvious recommendation for people either using AIX now or considering the value of a business relationship with IBM: think Linux on Power - and forget about AIX.
You get open source, you get a hot chipset, you get that IBM relationship, you get a clear future direction, you get a solid development community, you get access to lots of applications, you get an anytime escape to the cheaper Lintel world - and you get Sun covering your bets because what runs on Linux, can usually run on Solaris too.
All, as the mole sisters would say, great stuff - and really, not so LinP at all.