It’s going to depend on pilot preference, whether it is mounted or free and the information needs of the flight crew.
My personal preferences?
1). Keep em small - I personally like the iPad Mini for EFB duties. Small enough to attach on your kneeboard or keep free and it doesn’t block movement of the flight controls at critical times.
2) use a unit designed for cell network use with an internal GPS. Good for low altitude GA flying plus can be combined with an external GPS and you can use a cell network for data in a pinch.
3) when it comes to internal memory, the more the merrier. The Mini 2 has 128GB which is s good size for downloading all regional or national charts and plates.
I’ve seen a lot of people combine their tablets with Stratus, etc for anADS-Bcompliant unit. All nice but I would prefer a permanent panel mounted and certified unit for those purposes. I also would not get too comfortable with using the SVT features of Pilot, ForeFlight, etc as those are not certified for IFR use as well.