That rather depends on the card.
What you were suggesting was that he should trust his bank to give him the best card with the best deal.
Who on earth trusts their bank to give them the best deal?
Banks are just second hand money salesmen - they will normally recommend the best deal for them.
Most banks have a card that is specific for usage abroad.. he will have to see which one suits him. Some are marginally better than others, it would still be my first port of call. This way I always know I can transfer money over very quickly if need be.
We all know what banks are... you just have to use them to your benifit
Well using any card card abroad from any bank is plain stupid. Yes you can transfer money, it's great, what happens when you loose your card, happily bend over and apply vaseline to your anus???
To answer the original question:
The rate will always vary, today it traded at 1.2467, you can get €1=£1.2342.
Have 100 euros in cash and rest on card, there's no fee for paying for stuff and if it's stolen some of them will send you the balance via western union within 24 hours. Your bank will send you a new card to your home address, no use if you're 1000 miles away...