I actually use both.

FCview just because more people use it and I am able to see who I am working with easier. However its main feature I keep it for is the 30 update look back. You can go and see how your schedule changed over the last 30 updates, which is very useful when **** hits the fan.

Crewline I use mainly for the ability to swap/drop/add trips and see potential X list trips I might get a call on.

If someone would just combine the two it would be awesome but in all honesty, I have no issue with either and enjoy them both.