For starters, both the lenses you are talking about are fairly cheap so there is no reason to get rid of the 50mm to buy the 35mm.
I have a 50mm that came with my very first camera, before I knew much about photo

I didn't use it very long because, to me, it is not a very interesting lens. On the other hand, I almost always had a 35mm on one body. I kept the 50 because I wasn't going to sell it for much and if I broke my 35, I could use it...
Now, this is from the point of view of a film/full frame body user.
With a crop body, the 35mm becomes a fairly boring lens while a 50mm becomes a decent portrait lens. When shooting portraits, it is nice to have a little distance between you and your subject. It is more comfortable. These days, it seems like a lot of people want way longer lenses for portraiture but, to me, 85/100mm is great. A 50 is equivalent to 85 on a Canon crop body (somewhat different on a Nikon.)
I am not right on top of my subject when shooting but I'm not so far away that I have to raise my voice to give directions.
Hope that helps.