The first big difference between Sonar 7 and Logic Pro are the operating systems they work on. Sonar is Windows exclusive while Logic is Mac exclusive. Choosing between the two hinges on whether you already have a viable computer. If so, you will probably opt for the program that is available on your operating system. If you are buying a new computer to function as a digital audio workstation, consider the operating system with which you are familiar or prefer.
Sonar 7 and Logic Pro differ a lot in their respective interfaces. For most users who are not familiar with either program, the Logic interface is more user friendly. However, the Sonar interface has several rich features, such as saving track templates, which can enhance your production abilities once you learn to use them. Both programs have adjustable interface options, but Sonar's go a little deeper than Logic's in offering customization.
Logic uses Apple's AU plugins, while Sonar uses Windows only DirectX and VST plugins. Logic's out-of-the-box plugin suite gives you richer and deeper plugins than what Sonar offers. However, DirectX and VST plugins are more common than AU, so additional plugins are easier to find for Sonar. You can also find several free DirectX and VST plugins.
Both Sonar 7 and Logic Pro offer in depth editing and mixing features, but the workflow differs between the programs. Sonar's editing tools make editing more user-friendly than Logic's tools. However, Logic features such as track settings make mixing a little more approachable. In the end, both programs do editing and mixing well, so the decision boils down to user preference.
Logic has been a leader in the category of MIDI and loops for many years, but Sonar offers a rich array of features as well. Logic by far has the most sounds and loops out-of-the-box, boasting nearly 40GB in content. Logic also has some of the best software instruments of any audio software. Sonar does not have the library of Logic, but still offers a large selection of sounds. Sonar also has powerful MIDI features like the Synth Rack that allows you to layer several sounds and play them all with one key.