Note: Question is SPECIFICALLY to experienced day traders who have been day trading for several years and spend AT LEAST four hours a day trading.
If you're day trading full time and you have all the time in the world for it...and you can only choose one of those devices, which would you choose...and most importantly, why that one instead of the others?
Desktop tabs hands down. Mobile phones are not the same as laptops, the features are smaller if existing at all and can't perform a trade as fast. The advantage I find with desktop tabs is that you can monitor it better using different monitors and act right away - obviously this is not the case on a phone.
From my experience, phones are great but only for short-term checking and not so much trading.