Try opening a Biab file in Sonar
Here's the deal for me anyway..
I can do the realtrack generations in RB with much more versatility than BiaB (which makes it a 'plus' to BiaB)
Because of this (and the style versatility also) I always move anything from BiaB to RB to customize it anyway.
Once I am there, I can do *most* of what I can do in RB (without Sonar or any others) and still retain those generating benefits. So why leave yet? I keep on workin' with ease.
If I do find a job I need to do outside RB, I'll use the export features to get the tracks out and do what I need to do. But if I keep a current version in RB I can go back quite a long way at any point to rework something (like generate a new 'break' section at any time or add a section). I find those little conveniences very nice.
There are a few things in Sonar that are not possible in RB. There are many more (if you use the generating features) in RB that are not possible in Sonar. Depends on how you work I guess. I like being able to go back a year later and rework something.
Try it, you may like it