You can use both Claudiu. You can open up FL inside of Cubase as either a Rewire device or a Vsti. Cubase will handle the "finished product" a little better as far as doing the audio recording is concerned.

Even if you aren't good at making patterns, there is plenty of stuff out there to get you started. Listen to midi files that you like, for example, then import the tracks into FL and analyze them. You'll get an idea of what's going on and you can cut and paste the parts you like ( maybe a drum or bass line for example ) and create new songs. You should find this to be much faster than trying to write an arranger style from scratch.

AJ