Both are well made and basically the same so it doesn't matter which you choose.
The 870 has a short threaded mag tube end in which to screw a tube extension on. If you use the sling plate with a tube extension it will reduce the number of threads holding it on and you will need to use a mag clamp to help secure the tube extension.
This is not a problem with a 590 because it has a longer threaded end on the mag tube.
GC
The 870 has a short threaded mag tube end in which to screw a tube extension on. If you use the sling plate with a tube extension it will reduce the number of threads holding it on and you will need to use a mag clamp to help secure the tube extension.
This is not a problem with a 590 because it has a longer threaded end on the mag tube.
GC