"Performance Comparison For SuppressUnmanagedCodeSecurity Attribute"

>>> 60 repetitions >>> IN NANOSECONDS (1000ns = 0.001ms)
Method   Avg.         Min.         Max.         Jitter       Total
A        375,601ns    365,000ns    481,600ns    105,998ns    ! 22.536ms
B        275,173ns    270,400ns    334,000ns    58,826ns     ! 16.510ms


Code snippet taken from "P/Invoke Tips".