Hi,
I agree with NuBlue. I think it is easier to make the final transaction on your computer even if you may have done some research on your phone.
I would also think that I would be more likely to complete the payment through my mobile if the shops checkout accepted PayPal because this would mean I would not have to enter all my details in to the merchants website (address, credit card etc) on a merchants own checkout process on a mobile handset and instead could rely on the fact that this was already set up and stored in PayPal so all I was doing was entering my PayPal username and password and confirming the payment should be made to the merchant.