If you want to do rotary, and you or your parents aren't loaded, then you need to seriously consider the forces for your training. Rotary costs between 2 and 3 times that of fixed wing training, it can easily top £100k to get to the same level (CPL, ME/IR) if funding it all yourself. This could be a real deciding factor.
Which pays best? Generally fixed wing, if you go into the airlines. Job availability is more tricky, in my opinion you are more likely to get a job as a commercial fixed wing pilot when on low time (experience). Insurance often dictates things with rotary, meaning you have to start much lower down, generally speaking. 200hours on fixed wing and you can realistically apply for a FO jet job of some kind, depending on various factors of course.
I'm not doing the forces as I'm too old now, so I'm doing fixed wing and aiming to fly rotary again on my PPL at some point in the future, just for the fun of it.