Figure out what it is that FL 9 can't do that you need it to. Then you'll know what features you need to look for in a replacement DAW package.
At their core they all do essentially the same thing, allow you to capture and manipulate and build multi track audio
Other features vary slightly and some do some of the value add stuff better than others.
Once you have identified what FL is not doing for you it should be easy to pick a DAW with the full features you need
If FL isn't missing anything then don't bother to replace it just for the sake of getting something the has a more "pro" cache to it.
Once you reach a brickwall where FL can't do what you need it's worth looking for something new. If not your just taking time and money to learn a whole new DAW that may not do what you want either, once you've taken the time to figure it out
Go with what you know until it's not sufficient any more