I agree. I think the glass is super smooth and nothing compares to it's glide with the S Pen.
Personally, I use the Spigen.tR, but it was about the only one available when I got mine. The Zagg is new within the last couple of months. Previously they only had film screen protectors. I like everything they make (except those film protectors) so I was glad to see them come out with a glass option. I don't know much about the Nillikin, but the price looks good.
Whatever folks choose in glass, the rounded or beveled edges are crucial IMO. They ease the transition from the glass to the edge of the phone. They virtually eliminate chipping along the edges (which was a problem in older model protectors) and they make the transition super smooth feeling in the hand. They help virtually any case fit and like I said in an earlier post, the beveled edges add some sparkle (at least with the Spigen).
Anyone considering glass vs a plastic or vinyl film protector should watch the abuse video I posted earlier in the thread. I don't have even a hint of a scratch after months of use. They're worth every penny.