For what is it worth I am having the exact same considerations and just ordered the HP.
- Prefer 16:10 over 16:9
- Prefer 30" over 27" even if it just means that the pixels are slightly bigger (101 PPI vs 109 PPI) since horizontal resolution is identical. 2560 is a high horizontal resolution, so it's actually nice to stretch that just a little wider. Squeezing it in on a 27" is a little similar to users not really getting that much benefit from the iPad 3 and 4's high retina resolutions.
- No reflection issues (which are quite serious in most environments)
- Because it annoys me that Apple didn't just add a MiniDisplay-port to the Thunderbolt display and instead made them two different monitors. I would have liked a monitor that I could use both with my PC and with a Thunderbolt Mac.
I much prefer the design of the Apple Display and this was a major issue for me. But in the end it wasn't enough to sway me.
I am used to working with two 30" Samsungs side-by-side and the thickness of the border is about the same as the HP. Not a problem, really. From my visits in the Apple Store, I would say that the border on the Apple Display is actually a bit wider, but not excessively so, so not a major concern.