As a 'payment processor' they are somewhat different because Stripe is more for business, PayPal for individuals and small business.

PayPal is considerably more 'interventionist' with sales, and they seek to protect buyers etc so it can be a huge problem sometimes.

Stripe is more of a classical processor.

Of course Stripe does not offer a user oriented alternative to the PayPal product.

PayPal has many undocumented processes which make it very challenging to deal with.