I have several computers... Most of them are old junk. 1 custom built about 10 years ago. Nothing special. In storage now. I currently run a first generation Acer Aspire One Netbook. Although it is strictly offline only. Runs great, mostly video. 720p or lower. And a nice new Dell(I hate Dell, but it had a solid hinge and the best specs at Walmart. Sad I know...). Still nothing special. But as long as I'm not attempting to play the latest games, it runs just about anything I can throw at it. Most of my time on this site is spent with my phone. There are usually too many people around me when I have my computer out.
My previous and current laptop are pre-built but I only use them for work or when I specifically need the portability.
I use two custom-built desktops (i7 920 & 950) from back in ~2009-2010.
I also use pre-built dell i7-3770, which performs just about as well.
I only do custom builds when I really want to get something out of it. If I do another custom build it'll mostly likely involve quad channel RAM. Otherwise, there's plenty of pre-built deals with plenty of specs for your everyday tasks.
Desktop, custom. It last longer and is better for you ergonomically. Screen farther away/larger keyboard etc. Plus it's cheaper to update and has better parts for pc master race gaming.
Also, you can add multiple internal hardrives if you need more space, which are much cheaper and run better than external drives.
And putting it together yourself and maintaining it gives you a sense of ownership that's a nice feeling.
I'm actually using my Wii U, to be completely honest.
It's a little finicky some times (no adobe flash, can't play browser games, ect., ect.) but it's good on hand and auto-HDs everything. These things are surprisingly useful. σωσ