If you plan on using it a good bit as a portable, I'd go the laptop direction but in the next size down 13"-15". When I was carrying one daily a couple of years ago, weight & battery life were higher priority than display resolution/size.

I was running 1-2Ghz single processor w/ max memory & it was doing everything I needed while getting my civil engineering degree. It was 13x9.5 (HP 1000 series). The screen was large enough to not need an external monitor but small enough that it weighed about 5#. IIRC battery life was 3-4 hours or more with the extended battery.