I suppose first thing is to decide if you'd prefer a Mac or something Windows 8.1 based.
If you'd prefer a Mac, either and Air or 13" MacBook Pro with Retina screen, depending on whether light weight & battery life are most important, or you'd prefer the better screen.
If you are considering Windows devices, you could taka a look at Dell's new Venue Pro 11
line. You can get an add on keyboard with additional battery, and the dock is useful for when you're desk bound. The screen, a full HD panel is by all accounts quite good, and you have the option of an active stylus too.