I think this is a situation where a lot depends on your workload, you requirements, and your resources. For example, even if Solaris wins on performance grounds -- and I don't know that it does -- you may find that Linux supports a wider range of devices, and has better software availability. This may translate into a lower cost/performance ratio.
If you're really concerned about performance, the thing to do is set up your own benchmarks. Using the same piece of hardware, run identical tests under Linux and Solaris and see what you get...keeping in mind that the results are only relevant to your benchmarks (which means you have to make sure your bechmarks match as closely as possible your real-world requirements).
That said: if you're planning on a career in (or near) systems, learning how another operating system works is to your advantage. There are a number of things that I think Solaris does better than Linux...and there are things that I think Linux does better than Solaris. Getting a sense of the alternatives is important, because this broaden your understanding of the field.