Pros/Cons:
Desktop PC
* Easy to upgrade.
* Cheaper than a comparable performing laptop.
* Easy to change out parts, if you have a failure (goes with easy to upgrade a bit)
Cons
* Not very portable, unless you have a SFF PC and don't mind moving it now and then (assuming you don't have to lug around the Monitor, Keyboard, Mouse, etc.).
Laptop
Pros:
* Very portable.
* Generally nice for couch surfing and/or gaming on a flat surface (in order to get good cooling).
Cons:
* Not always easy to upgrade, other than RAM or HD (usually very difficult to upgrade CPU/GPU/Screen (if even worth it).
* More expensive to get good FPS on decent resolutions (assuming you have at least 1600 x 900 or 1920 x 1080 resolution).
* May not last as long as a good Desktop, because of the constant open/close of the system or even some poor cooling situations (i.e. in lap on couch causing poor ventilation).
It's up to you and what you want to do. I would love to have a $1,200-1,400 laptop to tote around for 99% of my tasks, but I don't have the budget for that. I know that if I put that much into a Desktop that I'd be good for at least a couple of years and then I would only need to upgrade a few parts (CPU - maybe, GPU, RAM, HD, & maybe the Monitor) and still not break the bank too much.
One final option. You could build your Desktop first and then when your ready for college (assuming that your going to go to college) buy a laptop for notes and most basic needs. Then you can come back to the dorm or apartment and use your Desktop for the intensive items. My son has this kind of setup and it seems to work well for him.