I recently replaced my 7" Samsung with an
ASUS ZenPad S 8.0 (Z580CA). First, it is an 8", but it is physically about the same size as most 7". They do this by taking the screen almost completely to the edge, whereas most tablets give you a 1/4 inch margin or more. This is fine if it is mounted in the plane, but when trying to hold it in your hand(s), it is easy to touch the screen, accidentally launching an app, or doing some other calamity. Second, the Asus is thinner and cheaply built. Again, this is fine if you are using it mounted in the aircraft, but it is not as rugged as the Samsung models (my old one, or the newer models). The ASUS is FAST, has lots of ram, the screen is as bright as my old Sammy, and can be expanded easily as can most Androids. It also has a pretty good internal GPS. Not as good as any of my old Samsung tablets, which would immediately tell me what room I was in on the first floor of my 3 story house, but in the same scenario, it is good enough to tell me I am in the house. No problem in the airplane however. It is plenty good.
All in all, I am happy with the purchase and very happy with its operation in the plane, but I know its limitations (cheaply built and probably easily broken) and I compensate by handling the tablet carefully.
Edit: I just re-read what I wrote and you're probably wondering why I didn't buy a Samsung like Jay did. I believe the Samsung is equal or superior in every way except physical size. I mount the tablet on the far left side of the panel against the "A Pillar" on the pilot's side, effectively blocking my clock and vacuum gauge, but still leaving the airspeed indicator and turn and bank fully visible. I would eat into the turn and bank and airspeed indicator with any wider tablet, and certainly with the 8.4" Sammy, so the 8" ASUS is the largest screen I could fit in the space available. You can look
here to see how I had my 7" Samsung mounted, and my new 8" Asus takes about the same amount of room.