I wish I could comment on the depth of midi editing in SO3. I'm a basic midi editing kind of guy.The midi functions it has does all I need it to do. I have read though that some who were using the deep midi capabilities of Sonar were disappointed in SO. This was a few years ago so this might have changed. This in no way means that what most probably do with it is inadequate. Might come up short for the deep user though. It all depends.
It takes just a little longer to scan my 500 plus vsts. That isn't a major thing for me. It doesn't appear to import mp3 files directly. Something I don't often do. If you need that though, might be worth looking into...or converting to something else.
The arranger in SO3 is second to none IMHO. You can easily move sections of arrangements around. I found this to be really helpful.
Their answer to the command console in Sonar is more sleek and where you get updates and news from Presonus.
They have a direct upload to Nimbit, Soundcloud, use of offline mastering links similar to Sonar. Mac compatibility, so if you work with a mac user you can share files directly.
I think their hardware is under rated here on the Sonar forum. With the addition of recent hardware acceleration latency times can be trimmed WAY down.
I think there is far more to like about it than not to like. I found using keystrokes for FF,RW, REC etc fast. I found the GUI layout easy to use if not a little small to my eyes. Everything is drag and drop. It's easy to add efx and sends.I use two monitors and that made it easier, but I think even on a laptop the opener page is easy to navigate.
I really like the way Sonar lets you customize the GUI. It seems more open and usable to a guy with bad eyes. This was one of the main reason I chose to use Sonar. Probably with some GUI customizations I could grow to like SO3 better.
One other thing I should mention. SO has album mastering tools not seen in most other daws. You can master an album complete with tags for upload. While Sonar has some decent mastering tools it doesn't touch the surface of what SO3 can do in mastering a project.