Special Purpose Tablet for Commercial Navigation app
I wish this site would embrace this topic because it is simply an extension of aircraft avionics and navigation. 

This question will probably be closed, but I think this is an important question that doesn't have any definitive answer on the internet. I recently went through the upgrade from paper charts to electronic flight bag. There is very little guidance (information overload) or standardization on this topic. However, it is helpful to look at what some of the large aviation operators use.

Several flight schools have specific recommendations for tablets. For example, 

ATP Flight School recommends the iPad mini, 32 GB, and Wi-Fi + Cellular for it's flight instructors. 

Directly from ATP: 


  ATP recommends the iPad mini, 32 GB, and Wi-Fi + Cellular (Available
  from Apple).


I've seen similar recommendations from other flight schools and Universities with flight programs but at the moment can't find the references (will update once I locate). 

Personally, I use an iPad pro because I was informed that it has better anti-glare properties on its glass than the non-pro version of the ipad, which is important for day operations in the cockpit. 

(Note, Apple lists antireflective coating on both the Pro and the Mini version of iPad but not the regular iPad). 

I have run several of the Navigation apps on android and iPads and noticed that they seem to be a little better on the iPads. Some even have more features  on the iPad versus the android (i.e. WingX Pro). 

Also, 32GB is more than enough (as of 2018) to run the navigation apps with all charts loaded and everything turned on including synthetic vision, assuming that it is a dedicated flight tablet and you don't have it loaded down with a bunch of other content such as videos, songs, pictures, etc. Also, you'll want to install just one navigation app, if you install multiple, and download all the charts for each one, it duplicates all the data and will use up your 32GB quickly.

I have ADS-B external antenna and it works just fine with either. The ADS-B I used creates a local wifi signal that the tablet connects to the antenna and all of the traffic and weather data is incorporated into the app. In other words, ADB-B data should work with any tablet that has wifi capabilities.