I've had the same computer for about 6 years now, my dad built it for me with stuff he got from craigslist. I recently got a job, and when I get the money, I really want to either buy a new computer, or build one. I just want to be able to run programs, such as Adobe After Effects, or Sony Vegas, without them being so slow. And I'd like to be able to watch videos in HD without my computer slowing down. I MIGHT get into gaming but I doubt it. Would a prebuilt computer be able to accomplish this? Or am I better off building one myself? And which would be cheaper?
It all depends. When I priced out what I wanted in Cyberpowerpc the price was reasonable, the only game changer was when I wanted to add another 7970 to the mix, in cyberpower adding the second card was going to be around $715 bucks or so.
I stopped, priced it out all on newegg and built it myself, the combo deals and discounts (along with 3 free games for buying a 7970) eventually worked out cheaper.
I would say the difference is that in one you will be paying more, but you won't be going through the headache of what it can be to build one from scratch start it up and go through all the motions. While the other, you can pay less, take on the task, and spend a while trying to get everything right. For some people it is a trade-off that they just don't want to handle building one.
So simply put.
Buy computer: less work, more money
Build computer: more work, less money