We have PC/Windows for internet use. I also have Mac for graphics and translation work. My Mac used to be on-line, until lightning hit.
My first computer (long time ago) was Mac, and I prefer Mac. The negatives are high cost and lack of local support. If you live in area where you can get real live support, and buy parts, then Mac is a good choice. If you don't know other local Macophiles, then it can be hard to find service help. If you are very knowledgeable about shopping on-line you can get good deals via ebay, but you really need to know your stuff so you don't get ripped off.
The other negative about my iMac was the built-in Ethernet. Lightning struck our Mac and PC at the same time. Roadrunner replaced the modem and Ethernet, no cost, on the PC. Can't replace built-in Ethernet in Mac, so I am stuck without internet.
Another neg about Mac is not as much variety for available software but that situation is improving. More software and hardware accessories are becoming Mac/PC interchangeable.
I don't know about Dells because our PC is custom built. I have friends with Dells, and they like them. The college where I interpret uses Dells for general computer work, and Macs for graphics work.
Dells have a wide range of prices and features, so it probably depends on the system you want.
It really depends on what purpose you need for the computer, your budget, and your skills.
