The Ipad is a " Jack-of-All-Trades." Good at everything, but not necessarily the best at any one thing. - BUT - don't take that as a knock against it. That's the nice thing about tech in today's world. There is enough of it, that you can pick the device(s) that work for you within your budget.
Theoretically a device that does one thing and one thing only, should be the best at what it does, but maybe you need a device that does more so good is actually best for you.
If you are very mobile, the Ipad maybe be too big and you might find something smaller more practical. If you just want to read and don't need extras, something like a Kobo E-reader might be just fine. Or, maybe you will opt for something in the middle, or multiple devices. AND of course, for alot of us, price is always a big factor. So saying something is the top of anything, is really more a personal thing.