Anonymous Vs Named Pipes

I haven't been able to track down a definitive answer on this, so I'm
hoping someone in this group may know the answer.

Does an anonymous pipe have any benefits over a named pipe? Does a
named pipe physically write to the filesystem that pipe resides in
(thus the speed of the write is dependant on the speed of the disk).
The reason I'm curious is if I know I have an IO bottleneck, will
using named pipes cause me to feel that bottleneck, or is it all in
memory like an anonymous pipe.

ie)
cat test.dat | grep junk 1>/dev/null
vs
mkfifo test.dat.pipe
cat test.dat > test.dat.pipe &
grep junk test.dat.pipe 1>/dev/null