I agree with sohum here. Believe it or not there is a considerable difference in the application and mentality needed for test and one day cricket. In test cricket, patience is the key and usually the more "talented" players succeed in this form of the game. But the one day game doesnt give you as much time to think and choose. You need to be in pace with the game.
West Indies would do well to score between 250-300 in a 50 over game but struggle to make totals above 500 if they were asked to play on. England on the other hand would take their time and get to a high total, but at the same time arent able to maintain a good enough run rate, which is needed in one day internationals.
The West Indies have a lot of these perfect one day players, especially in Bravo and Smith. They might not be the most talented players but are able to do the small things needed in their bowling spells and are get quick runs with the bat, irrespective of how they get them.