I use to use Sonar and had been for quite a few years. Great program. I moved to Cubase this year as I wanted a app that I could use on a MAC and a PC. If you are solely a windows user Sonar is a great way to go. I am very happy with Cubase and actually prefer it a little more than Sonar in some regards. There are still things I miss in Sonar. You can't go wrong with either.
This is a good shootout of top DAW's. It doesn't include reaper but has good information on many of the apps you will find in recording studios.
http://www.digitalmusicdoctor.com/shootout/shootout_summary.htm?PHPSESSID=9a048fc484bed1d69f25a4d61b76af96
If you are purchasing think not only what you are doing today but what you might do in years to come. Think about what is important to you, MIDI editing, audio editing? A lot of things to consider.