I think that you need to compare hardware on the structure and micron level.
Xeon Woodcrest Preys On Opteron | Tom's Hardware
ftp://download.intel.com/design/Xeon...s/25039702.pdf.
Then build an idea about how UNIX systems are put together. (well put together)
Unix File System - Wikipedia, the free encyclopedia
UNIX: System Design
Only then you can really give Solaris two thumbs up for Sparc/AMD hardware, and the same for Linux on x86, but not vice versa.
My personal history installing Linux Red Hat on Sparc ( and others like me who tried) is being disappointed at the lack of Linux drivers for SUN hardware. SUN still holds many of the Hardware design architecture proprietary. Thus giving you hard time with retrieval and display of data from and to I/O devices.
Great Raptor display cards, RPC units, SUN sound cards, and most importantly, the Oil fields equipment like quake sensors, ultra sound devices, and chemical analysis devices, fail to work with Linux, While SUN has given Solaris full armies of software drivers and applications for them.
Example; A few months ago an architecture firm requested me to check the possibility of migrating from SUN to Linux on their production line. They had pressure measuring devices that presses concrete cubes at 15, 28, 45, 60 days, until it cracks, giving the green or red light for a highway or a bridge to open or rebuild. I installed Linux on one of the hot swap drives, to find that Linux probed the massive hydraulic machines and installed them as a Xerox printers
. Calling the manufacturer Siemens® for hours and days to get the design of the circuit boards and internal OS data resulted in a dead end, as they have signed a deal with SUN to keep those kinds of machines internals proprietary. The suggestion to use the SUN CD driver that came with the machine as a platform to hack a new driver was not welcome at all, due to legal ramifications.
I think it depends on your industry.
If you are an ISP, Telecom, Education, Stock market & Financial, CAD Design (innovation of the individual is the core of the industry) go with Linux on x86.
If you are Oil, Chemicals, Conveyor belt, Health care labs, construction measurements (the machine is the industry's back bone) go with Solaris on Sparc/AMD.
Still, this is a humble personal point of view. I might be wrong.