Usually my laptop (so PC) tbh. I shamefully don't actually read comics with very much consistency, so it's not something that I do regularly on my phone during meals or wev. When I do read comics, a lot of the time it's on downtime at work while I'm at my computer still, or checking out series I see from the forums and such, which I 90% of the time are on via PC.
Further the app is kind of clunky to find comics with... I just said this on another thread, but I pretty much exclusively use my phone/app to read comics I'm already subbed to xD;;