I'v had the best luck with a newer iPad, personally.
I started with the Galaxy S2 from Android, but I occasionally would lose my video picture. Like literally the app would basically just cash mid flight, screen would go blank, and I would need to reboot the app.
A buddy let me borrow his IPad
Air 2 to test it out with a couple flights and I loved it. The video feed was much smoother, and nothing ever crashed on me.
So I did some homework. Found there was a newer iPad that was coming out in March 2017 that had a faster processor and brighter screen than the
Air 2, and it was only about $300. I scooped one of those new 9.7" ipads up and it has been flawless working commercially throughout a South Florida summer.
You will still need a sunshade for extra bright days, however. But that goes for just about any tablet not named Crystal Sky.