Computer sales people will try to sell you the most expensive model they can. Apple fanatics tout the clean design and ease of use of the Mac software. Microsoft users point out that they are in the majority and claim that Windows 95 makes just as good if not better. Both work fine. This is a matter of opinion.
Laptops are really cool, but cost much more for the same performance.
Get a desktop unless you plan to travel a lot with your computer. These days, either model is fine for Internet use if it is less than a year old. If you can afford it, go for the newest model available with all the bells and whistles. But if you are tight, take the bargain. Get at least 16 MB or even 32 MB if you can afford it.