If you're new to computer recording, trying demos may be a really steep learning curve, and trying to figure out what is best for YOU, may be difficult actually.
I jumped into Sonar because I use a PC, and wanted the best MIDI implementation at the time. I was previously using Adobe Audition, which lacked MIDI back then.
I think if you describe WHAT you'd like to be able to do, will help in answering your question as well and you may find you'll need some audio interfaces, that you may not have considered.
BUT...Sonar is typically very stable, as a lot of DAW software likes to crash, has a lot of extra stuff, so you normally don't need MORE software to get started. IOW it has drums, synths, FX... probably more than you'll ever use, but it is a complete package. Also it is a company that seems to really care about its' customers.
However, Studio One will be similar in many ways and can be a fine program too. I think Cake offers more in the long run. Also, these forums are a GREAT source for help figuring out things.