I don't trade coins though but I assume its less risky to stick to the coins that are already on top and has been traded regularly.
The great thing with yobit is that you can get free new coins to test its waters.
Indeed, if someones going to enter in this field, it is better if they will pick the coins that should be the one that is already on top of market so you can guarantee that the profit will be good. However, it is also better if they will take the risk of trading into other coins because sometimes they can be more profitable than to those top coins. The higher the risk the higher profit they will get.