Hi I have the 25mm/4 CV and a 21mm super angulon. If I had to keep one it would be the SA, as 35mm is my main focal length and 25mm is closer to that. Having said that, I love the 25mm CV and plan to keep it! It is true that it often doesn't give that "very wide" look, and can pass for a 35mm look. I find it a little too contrasty for my taste. The SA is less contrasty, and doesn't suffer from the "fat man distortion" / "football-shaped head syndrome" as much as many other superwides. A great lens, alas, quite expensive. I got mine cheaply (around 600 bucks with original finder), but it was badly fogged. Sherry Krauter cleaned it for 150 bucks and it's as good as new!
25mm + 40/50mm = good two lens combo
21mm + 35mm = good two lens combo
in my opinion...