It's easy! Not as much equipment needed! Everything is available ready to go!
It's expensive! (can's of extract cos 10 dollars or more compared to 2.05 for a pound of grain)
It can get boring compared to AG (all you do is play with powder and syrup! C'mon man!)
All Grain Brewing
It's cheaper than extract! Grains cost 2 bucks or less per pound. It's better to buy in bulk.
It's more fun!
You can really get creative with mixtures (think of cooking).
The only con I can think of is that it's costly as far as equipment goes.
You need a Boil Kettle, Mash Tun, Wort Chiller,False bottom, etc.
Once you go All Grain you will never consider extract ever again.