Yes, it is a big decision. The good news is you can't go wrong either way.
There is a 99% functional overlap between the two applications. The list of things one can do that the other cannot is actually quite short if you list them out. You can make a great record with either one (audio engine quality is not an issue). Both have helpful user communities. Both have lots of online resources available. Both products are mature and reliable. Both will require a significant investment of your time in order to master them.
Obviously, the folks who frequent
this forum have already made their choice and will mostly recommend SONAR, including yours truly. There are many here who also use a second DAW in addition to SONAR, mostly for convenience when collaborating with others. There's never been a formal poll, but my sense is that for most of them, SONAR is their primary platform.
One thing that distinguishes SONAR is this forum, which is open to everyone. We have a number of regulars here who don't even use SONAR at all, but hang out on this forum anyway to talk about third-party plugins, techniques, deals and bacon. I believe the congenial atmosphere is why you find such a high proportion of experienced users here, as opposed to other forums that are heavily weighted toward beginners who then move on once they don't need the forum's help anymore.
The other thing that distinguishes SONAR is the vendor, and the high regard they have for their users. Steinberg is famous for being indifferent to user requests and for imposing sudden incompatibilities. Unlike the majority of DAWs, Cubase and Nuendo require a dongle, which to me is indicative of the disdain the company has for its customers. Cakewalk staff frequent this forum often, including its principle engineer, who is not only a guru among gurus when it comes to Windows audio but also an exceptional musician and all-around good guy.