I have Skydemon on a Nexus7 with built-in GPS. It works but an external GNS2000 provides much more reliable GPS signal. The 7" tablet is ideal cockpit size.
I also have a Lenovo Yoga2 tablet in 10" size, you can get it in 8" as well; It has an outstanding battery capacity, I see 40 hours+ after a charge. It is very reliable and can be had for less than 200€. Try a big online seller and look for 'refurbished items'. The internal GPS is more performant than the Nexus7 one. It has excellent front audio speakers as well.
It used to be that the Android version of Skydemon was lagging in features compared to the iOS version, but this is no longer relevant.