I don't speak as an expert but as a keen Trike rider and I can tell you they are very good to ride, I find myself feeling much less controlled whenever I ride a two-wheeler now. Just being able to stop at traffic lights and not have to unclip is a great luxury. On the question of speed it often comes down to the rider. Obviously there is more rolling resistance with the extra wheel but also Trikes are generally lower down than two wheelers ( low racers aside ) so I find they are not that much slower. I have overtaken DFers many times ( even up hills on a few occasions ).
Don't have a Terra Trike I'm afraid so can't comment on that. I have an HP Scorpion which is fairly fast.