I've stayed at 5-6 Hilton (and associated properties) in Manhattan in the last few years multiple times. I always liked the big Hilton and was usually treated well. I did a lot of stays at the Doubletree as well and was always treated a little better. Its a less crowded hotel and a longer subway ride from where I was.

I usually ended up at either the Hampton or HGI on 8th. Always felt at home there, though its not the same quality as the big Hilton.