I have been reloading for the encore/contender for only 1 1/2 years but have been reloading for other guns for 15 years . From what I have seen It seems to me that if you neck size only ,the shoulder will move forward enough to cause problems with the action closeing properly and ignition trouble ( 0 headspace ? ) , shots stringing has also been noted . With that said I have recently started bumping the shoulder back .002 on resizing.
There are plenty of people around that may have more info than my limited experiance can provide.