Obviously, the big difference between the Apple product and the other tablet PCs is the operating system. The former runs the same operating system as the popular iPhone - the iOS, while the latter runs the complete Windows OS. iOS is strictly a mobile operating system and not the same OS designed for a Mac. With an iOS, you can only use its exclusive software system that's specifically made for a mobile device. If you use a tablet PC, on the other hand, you can load the same programs and applications that you can put onto your regular desktop or notebook PC. The only things that can limit you are your tablet's own limitations including memory and storage space.
The touch screen of an iPad is also different from other tablet PCs. It's called a capacitive type of touch screen, which works best for finger input. It's great if you want a highly responsive screen for your virtual keyboard input and other computer activities that require your fingers' interaction with the screen. If you're more comfortable working without a stylus, then the Apple product is for you. But this is not to say that you can't use a stylus on it, because you can purchase a specially designed stylus for it.
Windows-based tablets have resistive touch screen, which are quite the opposite of the capacitive type - more responsive when used with a stylus. This makes these tablet PCs a good choice for those who need handwriting-to-text functions.
Lastly, all the software programs that you can use on the Apple product have all been approved by the manufacturer, so you're sure that every one of them will run smoothly. Tablet PCs, meanwhile, can accommodate various programs, including those that may not be compatible with particular brands and models.
If you're planning to buy one of these products, even before comparing the prices of iPad and other tablet PC brands, the best thing to do is determine why you need it and how you're going to use it. In this way, you'll be able to know which brand and model will give you the best satisfaction.