For music related things, an ipad is allways the best solution.
All the music apps are available.. and support for apple models lasts 5 or more years.(android software updates about 6 months)

However, its not a cheep options, but also for apple goes you get what you pay for.
If i had to compare apple to a keyboard brand, it would be Yamaha
Where android devices varry from Korg all the way down to Medelli..