It depends on your workflow. iPad has been great for portable sketching and generating art – the images can be uploaded to sites. But you don’t have finer grained control over the files themselves (apple doesn’t want people playing with files). iPad also has limited storage, so you aren’t going to have a reference library on it which you might on your own computer. Getting the images onto other monitors or into different programs is going to be more problematic – if you need to take your piece into PS to do something – you have to get it over to your computer. I believe there is also only one decent choice for software – procreate (and you may be fine with that).
Having tried it, i knew it wasn’t for me – i like to have reference ahead of time, use different software (gimp) to color/tone adjust my reference , and generally like a faster interface (keyboard + pen) vs the pen only interface. I currently have a 13hd and mobilestudio pro. It was costly, but it has already paid for itself in illustration work.
If you have an apple store nearby, you might try it out yourself. Good luck! Do let us know which one you decide to go with!