Why don't you get the mid range iMac, it has a great screen and a great OS. However it gets very expensive if you pick many high end add ons and options.
Which every computer you choose, to solve that problem, you do have to do some research regarding external storage.
NAS - Network Attached Storage, you buy just the NAS enclosure, and then buy your own hard drives to stick in them, so how large the drive is, depends on your needs. But using a NAS also means you need to learn a little bit about RAID storage options and how to connect to them from your computer. But this is useful knowledge and worth the time to read up on.
Of course a simple external USB attached hard drive will work as well.
Here are some reasons why a Mac is great, built in Font library management with Fontbook, while it is by far incomplete, it is still better than what you get on Windows, which is Character Map. Fontbook lets you group fonts, enable and disable them, very handy built in utility.
Macs have great screens, sure you can buy a IPS screen for a PC just as well, but then the price difference won't be that large anymore, good IPS screens are expensive, although there are cheaper IPS variants today, you do worry about longevity because of the price, at least I do. Dell might be a good choice here, good availability (for repairs, relatively inexpensive, generally reliable).
Some things you may not care for, but I do love the dictionary in Macs, there are multiple language dictionaries on it.
Typing special characters is very easy, just hold down a key for a while and you get accented options for that character, and you can hold down option key to type a range of special characters not available on the keyboard otherwise.
You know, I can go on and on and there really are more to it, but I have get back to work ><