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  • Dustin Waybright thinks this is interesting:

As already mentioned, the less storage used, the less there is for a query to read, and the faster the query can perform. So variable length types are usually preferable in such cases when read performance is a priority.

From

Cover of Training Kit (Exam 70-461): Querying Microsoft® SQL Server® 2012

Note

Updates perform faster on fixed length where as read performs faster on variable length due to data size.