An iPad is not a Mac. It's closer to a cell phone than to a Mac. This is not to say that you can't use an iPad for recording—they're fine for scratch recordings, and could even be used for real recording if you can live with the limitations of whatever recording app you choose—but if you're expecting it to be anywhere near as capable as an actual computer (Mac or otherwise) running a traditional DAW, you're going to be in for serious disappointment for several reasons:
1. Although the CPU maxes out at somewhere around a fifth the speed of a laptop (according to Geekbench), it can't do that continuously because it is a mobile device with no fan. So there's a hard thermal limit to what you can realistically do with it in terms of CPU-intensive effects.
2. It has limited storage. It doesn't support external storage devices (or at least not for app use), and the largest iPad model's capacity—64 GB—is only about 2.7 days of continuous recording. If you're working with even two or three takes of a drum part that takes eight tracks at 24/96 per take, you can burn through that much space pretty quickly.
3. Only certain USB audio interfaces work, and not all features of all interfaces are necessarily supported.
4. The operating system, iOS, has no support for third-party plugins, period, so whatever effects your audio app supports are what you're stuck with.
There are probably other reasons as well, but these were just the first four that came immediately to mind. In other words, iPads can be great for low-end recording, but if you're serious about home recording, you should probably go with a computer instead (or in addition). You'll be happier in the long run.