It depends on what you are going to be doing with the rifle. The foolproof has click adjustments for windage and elevation, the 5D you loosen the screws, slide the carrier, tighten the screws to make the adjustment.
I have had a number of Foolproofs on various rifles over the years. I recently put a 5D on my Marlin. Once it was sighted in it held the adjustment alright, but it would have been easier to do if I had had the Foolproof.
Another nice thing about the Foolproof is that, once sighted in, when you change loads you count the clicks you have adjusted to be on target. Then if you go back to the original load, you just make the same adjustment in reverse to get to your original zero. Not possible with the 5D.
-WH-
