What I really want to understand is "why?" It'd be great if you could shed some light on the reasoning behind that statement.
Don't use raw input.
I actually had a similar system to your code prior to asking this question. And at this point I have the Raw Input solution, too. But I'm still deciding between the two.
I was actually leaning towards the Raw Input solution as it seemed more robust, but I'm seeing the "center" implementation more frequently in tutorials and such. After some Googling, I know at least the Source (TF2, HL2, etc) engine exposes Raw Input, but OIS appears to use the centering solution that you've suggested. Doom3 appears to use DirectInput, which is a (deprecated) wrapper around Raw Input. I haven't checked any other implementations, though.
Also: And I haven't tested this, but from what I hear, Raw Input allows you to make use of higher sensitivity in "gaming" mice.