SQL Server 2005 onward caches temporary tables and table variables referenced in stored procedures for reuse, reducing contention on tempdb allocation structures and catalogue tables.  A number of things can prevent this caching (none of which are allowed when working with table variables): Named constraints (bad idea anyway, since ...

Ask anyone what the primary advantage of temporary tables over table variables is, and the chances are they will say that temporary tables support statistics and table variables do not.  This is true, of course; even the indexes that enforce PRIMARY KEY and UNIQUE constraints on table variables do not have populated statistics associated with ...