There’s little to no difference in terms of functionalities and features these two types of products serve. If you get one, you might not even be able to differentiate which one is which since they look pretty identical and serve pretty much similar features.
Nevertheless, there are differences. If you avoided drilling the door, which is the essential requirement of installing a peephole camera, the doorbell cam is your buddy.
However, the peepholes come with an exceptional knock-detection capability pre-installed into them, which doorbell cameras strongly lack. For example, you can compare the well-known products by Ring, Ring Peephole Camera & Ring Doorbell Camera to compare and differentiate between the two and notice the difference.
We agree that there won’t be much to find out, but the main differences we just discussed will be easily noticeable.