Yes, Galaxy Note 4 is sun readable and I fly with regular, non-polarized sunglasses. Note 5 is said to be still better; Note 7 which I only had few days before the recall was phenomenal with the screen brightness of over 1000 nits and light sensors on both sides, front and rear, so that the screen kept the same brightness in circling. Now wait for the announced Note 8 to appear in August with the screen of 6.3 inches, probably.


Samsung Galaxy Note 4.
Daylight readable with polarized sunglasses
Internal GPS and barograph for backup system use.
Large very high resolution screen
many spares available
Recent android OS not obsolete windows CE type stuff - will be supported for several more years.
Wifi
Bluetooth
I used it 2 years with XCsoar and it worked great.