As you know G, you get a perfectly parallel neck. I used a wilson mandrel with my .308 for a while but then went over to Lee collet and Crimp. Obvioulsy as you say the crimp is not essential but helps in some cases wheer you are stick at mag length. With the .308 I was shaving tiny slivers of copper off of the bullets. Both solutions cured it but it made sense to remove a process.
I only use a button when FL resizing, apart from the 556 after the initial FL most of the time it is then neck only. I FL resize the 556 purely because they need to chamber 100% and quickly, then they get the collet so yes they may get over worked a bit but they tend to get used 5 times and then re-annealed and bunged into practice/SR loads (100 yards for standing etc).
The trick with these dies is to lube the cones so they dont stick, some suggest polishing them. I think it makes a difference what press you use as well. The forster floats and allows the dies to self centre which seems to work well with Lee (or any dies I have used).
Good luck with it anyway matey.