Android
Android has huge advantages in openness, file system access, and an ability to change launcher and default apps. Weaknesses seem to be audio latency, less quality games available, and less willingness by developers to make high quality pro apps.
Apple iOS
iOS / iPad on the other hand is a compute platform where it's been pointed out many times that the hardware is far more powerful than the software available. That said, apps & games on iOS are incredible and genre defying. Music creation possibilities are astounding. But the weaknesses - Apple limits other companies production of hardware, so there is little variation hardware-wise. But locking down hardware allows developers to rely on consistency, and then can build for a less varied landscape. The locked down file structure and software is very frustrating for some as well.
Amazing Games:
Magic the gathering Arena (both)
XCOM (both)
BattleHeart (both)
WazHack (both)
Heroes & Castles 2 (Android)
Amazing Apps:
GarageBand (iPad)
Drambo (iPad)
Koala (iPad)
AUM (iPad)
Turnado (iPad)
FabFilter Pro Q 3 (iPad)
FAC Drums, Maxima, Transient (iPad)
Various Synths - Mela, Mogue, Korg, and more (iPad)
