I think it's interesting how I feel about these two samples. I like the ME2 Trailer better than the film but I think the sound design is better in the short film. The sound design for the trailer seems to occur outside of the film environment. Thats the overall feel I get. Its as if I'm seeing this gorgeous imagery but the sound that accompanies it does not feel organhatic to the imagery. You have some muted high pitched clicks for the text that comes across the screen. I would bring that up. I would also re-think the opening sound for the Mass effect trailer. The diagetic sound of static is appropriate. But the non-diagetic sound of what sounds like the sound of smashing a chord on an electric piano is distracting. I would also choose another sound. Something that is not so hot. Pick a cooler sound. The action on screen is pretty serene. So instead of starting out with that harsh chord, select something softer. The sound design at the end of the trailer with the mechanical eye focusing on you should reach its peak with regards to tension. Also, there should be sounds associated with the movement of every one of those small parts.
In re-doing this, first work on the diagetic audio. Get the keystrokes or blips to occur with the text, for example. Then go over it with a selection of nondiagetic sounds to enhance the emotion of the piece. I think you have a good selection with that trailer. I think I'll give that trailer a shot myself. It's been a while since I did a sound replacement trailer and I need to update my reel! I'll share my work as well.
I only share my opinion as a fan of sound design! I still have a lot to learn technically, tho.