My first advice might be not to buy a computer at all. Why not a tablet? If you just don't like them or are doing more than just email and web then buy a Macbook. My Macbook Pro is 7 years old and I have absolutely no desire to upgrade. It's easily the best computer I've ever owned. Not even close. I've purchased laptops from every major manufacturer and they all were varying degrees of not very good. I used to spend a lot of my time diagnosing issues with Windows... now I just use my computer. If you want a desktop... then it hardly matters. Honestly . Again I really like the Mac Mini I bought for my kids. The HPs I use at work seem pretty good too, I just got an EliteDesk Mini. Although I would lean towards a faster hard drive 7200rpm in a desktop. It helps with Windows a lot.
Hopefully my rambling will help. Heh.