I will pray for both your friends, eric. If you look at it, they have the same problem: their former 'box of reality' is bursting at the seams, and they need to realize that they can live without the box!
I'd say for your atheist friend, tell him Buddhism will put him inside another box. Tell him of the black hole inside of him, that there is nothing that can fill the black hole, except for one Man. Anything he tries to put inside him to fill up the blackhole will only make him even more despressed, lonely, and alone. If he goes with Buddhism, he will only feel even more alone and will have to search for something else. There is only one Thing that can fill up the blackhole, the LORD Jesus Christ.
For your Catholic friend, tell him, about a vision I read about: There was a tall mountain, and from the top of the mountain there was a waterfall that lead down the crevasses into the lakes below. The problem with the lake at the bottom of the mountain was it was dirty, and the water sat there. Crowds gathered around the lake at the bottom drinking the water, and rejoicing to God for the dirty water. There was a trail that led up to another lake further up the mountain. The water was not as polluted but still stagnate. Some people were there, drinking its water. Further up the path became rocky, and led to a higher up lake, with fresher water. Few people were up there at such a heighth. Finally, there was barely a path, and to reach the top, a person needed to climb rope. But way up at the top, the water was rushing, and pure, and full of energy. Hardly anybody cared to reach the top, but those who did found the purest water and the most healthy water ever found.
The meaning of the mountain is it represents the world, and the water, it represents Truth. Straight from the source, Truth is the purest and the most beneficial. But as the Truth is spread out, the world dirties it with its own thinking, its own pride, the usual. At the second highest lake, God is easily found, but it is not the purest Truth that can be attained. The third lake is even more polluted, and the lake at the bottom is where the world drinks religion and self-determination.
Tell your Catholic friend to climb the mountain. God is beckoning.
God Bless You all.