Id agree on taking both visa and mastercard.

If you decide to buy something large along the way, Padi divers instructor course, a new car, plane tickets, etc. then visa is not very good because there is usually a limit pr. week whereas mastercard is unlimited.

Then better take two Visa cards since MASTERCARD RARELY WORKS IN WEST AFRICA.

Maybe there are limits how much can be spent via Visa card. I've never spent more than US$18,000 (that's eighteen thousand US dollars) at a time on any of my Visa cards, so I'm sure I wouldn't know.

Are the rules different on European-issued Visa cards? More to the point, what will you do in West Africa (the OP asked about Mauritania, Senegal and the Gambia), where your Mastercard is often worthless?

Is it really necessary to have this debate again?

Mark