How it (Mixbus) sounds will ALWAYS be a matter of taste I'm sure.
I happen to like it a little bit better than SONAR is what I believed to be a simpleton's test.
In another (actually my first) I took a 16 track song that I had previously mixed and started both a new Mixbus and SONAR project. I imported the 16 "raw" tracks into booth projects. Set everything to unity and then mixed the song in SONAR. Then taking note of the levels (-2db on guitar, -6db on the vox etc) I set Mixbus levels identical to SONAR.
Then I exported both as 24/44.1 wav files.
So remember, there are no EQ changes, no compression, no verb. NADA. ZIP. NONE.
In an A/B test I found that Mixbus "sparkled" just a tad more than SONR.
YMMV.