Best approach to remove time part of datetime in SQL Server

Which method provides the best performance when removing the time portion from a datetime field in SQL Server?

a) select DATEADD(dd, DATEDIFF(dd, 0, getdate()), 0)

or

b) select cast(convert(char(11), getdate(), 113) as datetime)

The second method does send a few more bytes either way but that might not be as important as the speed of the conversion.

Both also appear to be very fast, but there might be a difference in speed when dealing with hundreds-of-thousands or more rows?

Also, is it possible that there are even better methods to get rid of the time portion of a datetime in SQL?