How Does Sonar Compare To Music Creator?

MC6T is based on X2. Here is a comparison matrix between MC6T and X2 http://www.cakewalk.com/Documentation?product=Music%20Creator%206%20Touch&language=3&help=Comparison.html
 
The feature matrix for X3 is here http://www.cakewalk.com/Products/SONAR/Versions. With X3 the basic version has essentially the same features as Studio/Producer except for AudioSnap, ProChannel, SMPTE/MTC and Surround Sound support. Aside from those features the differences between versions are primarily the bundled plug-ins.
 

MC6 is almost like a cut down version of Sonar. It is a natural transition and would not feel alien at all.

To everybody, thanks for the comments.  I'm currently using Music Creator 6.  I found this screenshot on a blog here and most of it looks familiar (is this an accurate screenshot of the common layout?).  I think this answers my question.  I would have some more to learn, but I would find the environment familiar and I could probably get started quickly.  Thanks again.
 

The OP's question gave me a chuckle because I started my Cakewalk journey with Guitar Tracks, then began using Home Studio... when I asked a friend about SONAR, their reply was, "SONAR is like Home Studio on speed." I began using SONAR at SONAR 4 (PE).
 
For you, SONAR will do everything that MC does, just a "wee bit more" (understatement). SONAR will still import my Guitar Track projects (.wrk files!) without issues... the only "issue" is that very old effects need to be in the computer, and some 32-bit plugins/effects will not work in 64-bit SONAR. Up side is you can install both versions of SONAR (if necessary) on your machine, but I have stuck with 64-bit only. Opening an old project may give messages of "Plugin X (or Effect Y) not found" but the MIDI/Audio data is all there... you just need a comparable plugin/effect to replace the old with (and there are many bundled with SONAR). If you are running MC in 64-bit, this will be transparent to you since those effects are on your machine already.
 
Bottom line... get the SONAR X3 demo and give it a whirl... many things will be identical for you, but there is more you can do. If you are concerned of issues, create a manual restore point prior to the install, and you can always back out to that restore point if necessary. Stick with functions you are familiar with at first, and go from there.
 
This forum has a lot of very talented and experienced folks who give generously of their time to help others. If you hit a snag or have questions, simply ask a detailed question and you will often get a very prompt detailed response. I personally have not tried many others DAWs, and bought none of them, since this forum is by far the best resource to any SONAR user....