While we're not seeing a lot of purple finches around the US right now, it's always good to brush up on your bird ID knowledge. Here is a good comparison between these two commonly confused species. You should primarily focus on the lack of distinct stripes on the body, the raspberry tones in the purple finch wings, and the facial coloration and pattern. Male house finches usually have a gray ear patch that lacks any reddish color, whereas the purple finch usually has a really distinctive pattern covered in raspberry.