I just finished playing xcom on the iPad yesterday and honestly I would play it anywhere else if the option is available to you. There are numerous irritating omissions: missing cutscenes (autopsy, interrogations, research), neither of the dlc side missions are present and limited soldier customisation.
By far my biggest problem though was the camera. I spent more time fighting it than the aliens. Excruciatingly slow scroll speed compounded by a lack of inertia, zoom level resets when switching soldiers making the claustrophobic default intolerable and negotiating between interiors and exteriors is unbelievably more aggravating than on pc.
You would be far better off getting invisible inc instead. It's cheaper, it runs on ios11 and it's a flawless blend of stealth, hacking and turn based strategy married to a timeless aesthetic.