What separates pro tools from reason and fl studio is the way it functions. The result is that only in pro tools you will have exactly the same sound when you render your song and when you play it in program(Have you ever had a situation when you render your beat and have to go back to program to fix some levels or something).?
That's why all professional studios in the world use either pro tools or logic. So if you go for mixing and mastering pro tools is a way to go. Even if you just mix hip hop which has much lesser channels than other genres of music.
For the beatmaking (what we all use daw's for) fl is my choice because it is simple and much better than cubase or nuendo when it comes to visibility and practical use. Not to mention reason which has nice vst's but it is pain in the ass to use it. And fl has really good sample editor(edison) much better tham cubase or sound forge for cutting samples.
It all depends for what you need and what you're used to in the end. But if i need something to mix and process vocals i would definitely use cubase or pro tools over fl.