I feel like an 13" MacBook Air is the ultimate in flexible work environments. Incredibly light, powerful, goes anywhere, long lasting battery. Perhaps I'm just a philistine and haven't yet gotten a taste of the new world yet...
I have gone both ways several times.
Being able to group apps and then being them to focus on the single display works fantastic!
I took the time to get seriously productive in either case. The difference was not a big deal.
Chances are the OP rocks it as hard as they can. I was able to.
And being mobile these days, being able to work on an Air is a real plus!