Without knowing the underlying indexes, not really. It's not the syntax, the optimiser's smart enough to convert the forms, it's going to be the indexes that make a difference.
Without knowing what you have, this is a guess, but I'd put one index on sales.date and another on sales.prod_type, sales.date and one on customers.cus_no. That would be a start, I'd use the exec plan to tweak from there.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability