Hm, I could not reproduce that difference, and there's no reason at our end why there should be any difference, as that is determined solely at PayPal's end. Were you receiving checkout payments at the same PayPal Email when testing both cases?
There's a setting in your PayPal account (Profile > More Options > My Selling Tools > Website Preferences > PayPal Account Optional) that determines whether your buyers will be required to use a PayPal account of their own. If you have set PayPal Account Optional: OFF, your buyers will not be offered the "Don't have a PayPal account?" option to pay with a credit card on PayPal's checkout site.