And yet the SHIELD is getting Lollipop next week. So not exactly a big advantage going direct from Google.
The SHIELD's antennas frankly suck a bit. They're supposed to update the cellular modem, we'll see. Cellular connectivity rots. WiFi is OK but a little on the weak side. I still love the thing but those are serious issues with it for some (I could care less about the cellular).
You forgot some things that give the Shield tab a disadvantage:
I don't have a N9, but the N7 2013 still does some things better.
N7 - screen is brighter, sharper, and colors are better (white is white not gray or brown)
N7 - Screen mirror to Chromecast.
N7 - Slips into pockets better.
N7 - Runs Xcom for android
N7 - GPS picks up more satellites in a shorter amount of time.
N7 - lower price and 32GB
N7 - Camera focuses faster and handles exposure adjustment better.
N7 - Supports photosphere. (The ST has a gyroscope, but the Google cam app crashes when trying to use photosphere.)
ST - front facing speakers (not louder or better, just facing the front.)
ST - stylus is awesome!
ST - bigger screen
ST - HDMI out
ST - SD card slot
ST - 5Mp front camera (but who cares)
ST - Faster CPU/ GPU by a mile, but I don't notice this much.
ST - WiFi direct game controller and cool controller games.
More later as I use it.
Edit: new update for ST that came with Android 5.0 -
GPS now locks properly
Google camera app now works in photosphere