I think there are two major categories of DAWs out there today. Of course, some cross over these lines, but here are my thoughts. This is not intended to be a complete list, rather an example of my thought process as I look for a possible Sonar replacement.
I either own, or have tried a demo version of, everything listed here except for Bitwig and Logic.
1. Traditional DAW - linear track timeline with a deep toolset for recording, mixing, & mastering a music project. Modeled on the traditional tape based recording studio and console workflow.
2. Music making DAW - a toolset that inspires music creation on the computer, often with a non-traditional UI and workflow that does not necessarily have the steep learning curve of a traditional DAW. Very friendly to in the box production. But you may still need a full DAW to finish a professional project. I don't think you will likely find a fully satisfactory replacement for Platinum in this group. But there is nothing wrong with using more that one DAW in your workflow. And I'm sure some folks are very happy with only one of these, rather than the other type!
Category #1 examples: Sonar Professional/Platinum, Cubase Pro, Studio One Pro, Reaper, Logic, etc.
Category #2 examples: Cubase Elements, FL-Studio, Reason, Ableton Live, Bitwig, Tracktion, Mixcraft, etc.
So what I suggest as you demo other products, realize that it is a short list of full Sonar replacements. And none of them are likely to have a 100% workflow that you are used to with Sonar. Switching DAWs, or adding secondary DAWs, always requires an investment in time and frustrations as you climb the learning curve. Don't blame the product for being different from what you are used to. Blame Gibson!