Defnitely MacBook. How could you even consider a <shudder>Dell</shudder>?
OSX is great, the included apps are great, the third party apps knock the socks off anything on windows (devonthink/writeroom, etc).
The screen size is easily acceptable to me - I've been using one for about 2 years, switched from a 17" powerbook which I considered too large for travel.







