If I had to choose between the two, I would get a Murphy bed. I have yet to encounter a comfortable sleeper sofa…
Some ideas on what it would look like:
http://ithomedecor.com/ideas-of-murphy-desk-for-decorative-items.html/murphy-bed-desks/
One thing to consider: if one of you needs the desk to work late, the other can’t go to bed early.