Both are House Finches. Purple Fiches will not have the streaking on the underbelly and will have a triangle shaped beak as apposed to the roman nose type beak of the house (curving upper mandible).
Diet and plumage age has a lot to do with how bright both finch species are. So looking at their beak shape is the best visual que to what species they are. The first house finch image has a feather issue. Possibly mites (as they thrive on the head as it is not possible for the bird to preen there), which is a common occurrence in finch species.
I recommend the Sibley's Guide to Birds if you are serious in identifying birds. It is currently the best bird book on the market for North America.