which one would you choose and why?
it depends on where you are on your musicial journey...
are you a sample based composer or non sample based composer?
do you currently know what involved in making a song/beat?
do you know the different aspects of production?
i.e. making a song/beat, mixing and mastering
basically, there are tons of questions that needs to be answered before deciding whether to use/get fl studio or reaper....
but if you are just starting out start with fl studio. learn the first step of production which is making songs/beats and dont worrg about mixing or mastering until you could make a song or beat...
fl studio is a great program for beginners to seasoned songwriters/beatmakers. reaper (imo) is more gear towards exprienced songwriters/beatmakers. what i mean by this is individuals that write songs/beats, mix and master. you can mix and master in fl studio but compared to other DAWs it is not so straight forward (imo).
so, before you purchase anything find out where you are on your musicial journey. do not yeast up where you are on your journey because you will be only fooling yourself.
the bottom line with DAWs is that before your musical journey is over you would have gone throught must DAWs anyways looking for a workflow that suite you.
the key when starting out is learning what it takes to make music and not what DAW you are using because they all basically do the same thing (record audio and midi data)...
p.s. the point about on-line tutorials is good advice too. there are tons of fl studio tutorials out there. once you learn the concepts to music production you will feel at home with any DAW