You can calculate the depth of field using this :- http://www.dofmaster.com/dofjs.html
At 200mm you have a tiny depth of field to play with wide open, you have a better chance of cropping a wider fast prime lens but a 50mm will need good light to freeze the action, and the depth of field is shallow at 1.4.
@Airhead started
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You can calculate the depth of field using this :-
http://www.dofmaster.com/dofjs.html
At 200mm you have a tiny depth of field to play with wide open, you have a better chance of cropping a wider fast prime lens but a 50mm will need good light to freeze the action, and the depth of field is shallow at 1.4.