Those who use iPads have access to some good tools and the support of Apple Pencil. Apple do a lot to customise and optimise workflow with respect to their ecosystem.
I don't know whether we have any good alternative to what iPad and Apple Pencil does together in graphics workflow.
I have used both of them and I can confirm that they are very good for graphic design work. The most important thing is for you to go for what you can be able to afford that you should go for.
I have always made use of Windows in doing my design works. I think this is basically as a result of being able to have used my computer for a very long period of time and have mastered some of the things that are on it.
As someone who has used both Windows and Mac, I will admit that I prefer Windows. I remember I had to use a Mac back when I worked in a school and I struggled to use the system as I was so used to Windows.
If you're using Android and Windows devices, I think that Samsung S Pen is a very good alternative which comes very close to what you have with Apple pencil. It's compactible with Samsung Galaxy Tab S series and Galaxy Note series.