OSX- will upgrade from Elements slow performance?

At the moment, I’m running Elements 7. It’s pretty fast, lightweight and everything works. Doesn’t even require a dongle.

However, there are some features that are missing from this version which I would like to use - e.g. side-chaining, FX Channel routing, etc

If I upgrade, I’m concerned that performance will be slower, buggy, etc.

Where can I get performance stats for the different versions?

There is a detailed comparison on the Cubase Lineup page. I don’t think you will find anything comparing performance (I could be wrong) because they use the same engine. Because the full version can support more tracks and has extra features like Vari-Audio, then, of course, you may see a performance difference due to the size/complexity of your project (not because of the version you are using).