I would rather use a mixer for a couple of reasons. First of all I would rather spend the same amount of money on an interface with just a couple of inputs. That way you will know you are getting best quality ad/da conversion possible. You can buy some pretty good converters for that money. Secondly I would prefer to do some of summing through an analog mixer. And for individual tracking into the DAW, the mixer providing its own influence in regards to colouring and EQ etc.