IF you only want it for internet browsing/emails and stuffs like that (since you are a photographer even download pictures to it and see them a bit bigger than a camera's LCD) netbook will do ok.
However I could not justify going for notebooks that will cost more than $400-500 usd (netbook+upgrades,) since you would be approaching to MB's price ($900-999 for the white one.)
Also if you want Mac OS X in a netbook, then just go for a MB because now you can install Mac OS X on the netbook, however this doesn't mean that it wont have trouble in the future, and believe me troubles almost always happen when you less want them to happen.
White macbook = 5pounds
MSI wind = 2.3 pounds (half),
therefore a macbook is about 2.5 pounds heavier (or about 1L bottle of water)
Resume:
Money no problem?
You will use MAC OS X (either if it comes with MB or if you make a hackintosh)
You need a bit of performance (e.g. you are going to do something else than working with plain text and static images such as web-browsing, text edition, emailing)
You want maximum compatibility with an already existing MB/MBP/iMac in your possession
then buy a MB
You need an inexpensive system that wont matter if it breaks apart.
You are going to use it just for simple stuff (e.g. mail/internet/etc)
You are not going to replace any component (e.g. stock HDD, extra ram, etc)
You are not going to try a hackintosh (if you still want to go ahead with this, take a look at dell 9 mini, some people have had better results making a hackintosh with dell 9 mini than with MSI wind.)
You want to save every single pound.
Then buy a netbook.