I think the most reasonable comparison would be with Square, and it's a question of marketing. While Square has p2p payment features it's marketing is mostly to

I think the most reasonable comparison would be with Square, and it's a question of marketing. While Square has p2p payment features it's marketing is mostly towards businesses with its tagline being "start selling today" right on its website. Venmo's tagline is "share payments," indicating they're marketing themselves mostly for p2p. Paypal is a bit of a pain to sign up in comparison with Venmo, which allows seamless Facebook Auth via your phone so is easier for people to sign up for. Kind of all irrelevant since Paypal owns Venmo anyway, but there you go.