Mass Effect universe? that would be pretty kool to work with Commander Shepard.

Depends whether it's Paragon Shepard or Renegade Shepard. I'd probably want to stay out of his or her way, myself.

As for the rest of the universe - a science fiction setting is usually a big plus for me, but it's looking like there's a science fiction armageddon coming in the near future there. So it's not quite an obvious choice.

Darkspawn are gross.

Both settings are fraught with death and destruction. But in between massive world/universe threatening events a sci-fi world is just more comfortable and filled with cool advanced conveniences. They would both be quite dangerous from time to time, and you might get killed. So why not pick the one that's nicer in-between.

<Future with hundreds of aliens, and space travel.
>medieval time with monsters, dragons, and Magic.

Space FTW.

Just ONE murder? So not worth it... not enough to bring about a WORKERS REVOLUTION!!! Mass Effect it is.