JOIN Performace Vs. Multiple RersultSets

Can anyone give me some guidelines as to when to chose JOINS over returning multiple resultsets in a strored procedure..

For eample, I have two tables, Orders and OrderDetails, which are linked by a primary key field. There can be orders w/o a corresponding record in orderdetails.

1.) I can return all orders and their details using a stored preocedure that has:

   SELECT o.order_id as OrderId, o.customername, od.order_id, od.orderdate FROM orders AS o LEFT OUTER JOIN orderdetails AS od ON (o.order_id=od.order_id)

2.) I can do the same by returning two results sets in a different stored procedure:

   SELECT order_id, customername FROM orders

   SELECT order_id, orderdate FROM orderdetails

I think the client processing time for the second option will be slightly less, because the resultset I need to filter will only be as big as the orederdetails table (it will not include records for orders that have no details). Regardless, I think this would only make for a small performance gain, so if Option 1 is better in Database performace, I would probably go with that.

I assume the method to choose also depends on table size and # of JOINS. Any guidance would be appreciated. Thanks,

Al