We are not MAC people, so I'll offer what I've learned about the PC world.
There are some better brands than others....but really it comes down to the type of processor. An Intel Pentium is MUCH better than the knock off AMD.
I'm currently researching the best computer to buy for my work, that has to be a desk top. I recently went through this to buy my laptop.
First, the difference between the laptop and desktop. The desktop has more ports for various things. At work, we have a scanner that needs to plug in to the computer.....it would not work without an adapter in a laptop. A desktop also has the feature of if you spill something on the keyboard, you potentially are only out a keyboard, and not a computer. The laptop is very convenient of course, but has a better chance of being damaged.
While searching for a computer my minimum requirements are:
*Intel Pentium processor of an i3 or better. If it doesn't have an 'i' in front of the number, it lower than an i3, and you should google it to see where it ranks. This will make the difference of your processing speed.
*4 GB Memory or more (A 2 would be ok for light use, but 4's are very affordable). This also makes a difference in how fast your computer works.
*500 GB Hard Drive or more. This part isn't as necessary as being so large if you have an external hard drive. This is the part where you store all of your pictures ect. A 350 GB would also be fine for light use.....and if there is extra storage in other places.....but many people do not come close to filling this up.
*HDMI port
You should have an external hard drive of 500 GB or 1 TB for system back-ups anyway.
The price for a laptop that has all the above is around $500. The price for a desktop (not including monitor) is around $400. Monitors are around $100 - 200.
I bought a Toshiba 750 Satellite for $370 that had an i3, 4GB Memory, and 500 GB Hard Drive on sale at Best Buy last November. It has a built in camera, and has an HDMI port (a must these days).
I found a Lenova desktop today at Best Buy (becoming popular, and my husband in IT uses one) with a lower than i3 processor (by a hair), 6GB Memory, and 1 TB hard drive for $379. The monitor is another $150. Most desktops come with a keyboard and mouse.
I've found Best Buy to be very reasonable, Walmart to only offer the knock off stuff, and www.tigerdirect.com to be ok.....but it has to be shipped....which is usually free.
I also found that Best Buy is cheaper in college towns than at other locations. I saved $40 on my computer because it was in a college town. I paid for it where I live and picked it up at another location where they sold it for more....of course I had to ask why. :)
I hope this was useful. :) Have fun shopping!