If I ordered of you and selected PayPal as the payment method, I would expect to go to the PayPal website to complete payment. If the PayPal page came up, but the address bar still showed your domain I would not enter my PayPal/card details, and go elsewhere.
how is that different than customizing the hosted payment page?
when you actully get redirected but you customize the payment page to make it look similer to the website?
Because when you customise the payment page the domain in the address bar is PayPal, but with your way it would show your domain.
I would not proceed with the payment because I would think you have either been hacked, or you are trying to get me to enter my PayPal details on your site so you could gain access to my PayPal account, either way you would have lost me as a customer.