Flat Screen TV vs. Projector for in in person client sales sessions

Plasma screens   will have a better black level but do not handle more ambient room light as well. LCD screens  especially  if you go with a full array back light LED types will get close to plasma screens for black level but will handle more amount light better.

For projectors, Epson make good and affordable units that   can also handle more ambient light than  many.

But again IMO  do not worry  so much about ultimate   colour  fidelity of  either because you  are not going to edit on any of these, only  show and sell  from them and the clients really would not see if a screen is not 100% perfect in  calibration.