Definitely on my PC. I do not trust opening acess to my smart phone, nor do I want to take up space on it with poker or casino rooms. Thanks for asking!
I play on a desktop with a large screen. And I sometimes wish I had an even larger screen. I doubt if I could be bothered playing, if my only access was via a smart phone.
Of course the computer is inferior in many respects to the smartphone, but still the computer does not replace anything you sit at home you play poker calmly drink your coffee, for a smartphone the usual screen of hands is too small, of course if someone called you to work later, and you have a tournament of course you do not take the computer in the subway, the smartphone will solve all the problems))
Computer for sure. I like being able to multi-table, as it holds my attention better. It's more convenient especially because I have access to Pokertracker as well.
I use the two, because if the internet falls, I have the mobile 4G connection, on the PC it is better because you can do the annotations on the table, and the iphone does not.