From an end user perspective, Paypal is a service which magically sends money over the Internet, and you're near-permanently logged into it, so you can pay for anything with almost no friction after you use it for the first time. A Stripe dialog is just a form/modal you see on a website asking you for your credit card details.

They're similar services when you break them down, but Paypal is almost more like a social network for users, with accounts people may re-use dozens or hundreds of times over a year to pay for things. Many end users probably have no clue what Stripe is and just see a generic Web 3.0-looking credit card form (probably ignoring reassurances about how the merchant website doesn't actually receive the card data; that stuff goes over many people's heads, or they just don't even notice it).