I played E9th/B6th universal for most of my 'bar' playing career, I have since gone back to the doublenecks & really like the open notes much better on C6th than B6, just seems a whole lot more 'usable'. The guitar players hate the key of 'B', and many of my solos use the open notes. Of course thats just my opinion. I used to play steel guitar rag in Eb & B, & it did not make those guitar player happy!! But really, is that what its all about??
When I started up again in 1995, I seriously considered Universal, so I figured that the learning curve would be easier than having to unlearn C6. Well I never liked Universal but found out there are many things about B6 which work better for me. Blues with guitarists for one thing. Nice fat open E's for example. I like everything about it and it works better for music theory inside my head. It was only hard when I read tab, but even that has become automatic for me. I can't really see a reason to play C6 at all anymore. Unless it sounds better to YOU. What is important is "does it work for YOU?".