I highly prefer a computer (desktop or otherwise), but my phone is large and powerful enough to be a decent on-the-road alternative.
Using teamviewer, i can use the power of my desktop, as well as software that my phone just won't take, using my phone as the input device, and when it comes office applications (word, excel and the like), i use the available clouds to seamlessly transfer.
I am looking at getting a decently sized tablet for some options (including reading my digital, excel-based D&D character sheets), but the phone is a good option all-round