Trying to book a few LCC flights in Europe using the info found on this site about skyscanner.net and dohop.com and have a

1. On Skyscanner, updated for "live update" I get Iberia flights at E 32.72, E 41 with tax, but I cannot seem to buy through skyscanner. Seems I need to go to the airline website to buy the ticket, but there the ticket is E41 and E 58.72 with tax. Is skyscanner wrong or am I doing something wrong?

2. Is it better to use my Visa card or AmEx card to book these flights and the hotels (cash rebates not withstanding)? Do all Visa cards charge the same on the exchange rate or is it by individual bank?