The proper opening bid for west's hand is 1S.  It is almost always correct to open the highest ranking 5 card major when holding two five card suits.  The strength of the hand does not effect this opening bid, unless it is strong enough to make a strong 2 club bid. 

 

The only real exception to this is when holding 5 clubs and 5 spades.  There are many opinions of the proper bid with this holding.  It's a subject to discuss with you partners.

 

Change this hand to 6 diamonds and 5 spades and it would be proper to open 1 diamond.