Practical difference between SPARC vs x86

Some would argue the metaphor stillholds true, others would argue otherwise.

There's clock speed, but you also need to factor in RISC vs CISC.

What people get, or hope to get with SPARC, is a more stable platform with less downtime. Tecoms were historic SPARC consumers due to nebs compliance.

As noted in comments above, it scales better, so you'll tend to see larger systems. Along with possibly products that require more resources. ie: A database in memory. Some of the newer SPARC CPUs are also much more power efficient -- power and cooling is a big deal in datacenters.

Someone noted "software in silicon", in the comments. Oracle expanded on Sun putting crypto units in the CPUs, by adding database instructions, and plans on adding features.

In the end, the architect(s) will determine what is needed for the system. Chances are it will be a mix of solutions that best meet the requirements.

On the CPU cost. AMD has kept Intel in check over the years. Oracle appears to be trying to be cost competitive to x86, as well as it's RISC competitors.