The best overall lentils are Green Lentils, usually from France. I've never seen green lentils from the US but I'm sure they are available somewhere.
I use the red lentils for salads. You only have to cook them for a few minutes, then drain and cool them down. Add whatever veggies you want - i.e. celery, tomatoes, bell peppers, cucumbers, etc, and stuff them into avocado or tomatoes.
The brown lentils are good for every day stuff. I make the best lentil soup with Italian sausage. These lentils are great with tomatoes and any kind of sausage.
But the green lentils stand up the best to cooking and have the best flavor - at least to me.