I'm looking to buy an iPad, but can't decide which one. I'm an artist?

I'd love to have the iPad Pro, for it's strong supports with art apps and the Apple Pencil. But of course, it is $300 more than the Air 2, plus $100 for the Pencil.
I've seen people use apps like Autodesk Sketchbook Pro on the regular iPad (which has no pressure sensitivity) and do some pretty okay drawings. I'm not looking to create complete masterpieces on my iPad, just be able to sketch and paint on the go and feel comfortable doing so.
I have a drawing tablet for my computer, so that's what i am used to.
Will the pressure sensitivity make a big difference on the pro? I know it's pretty useful on my tablet.
Also does the speed of the iPad come into play? Will an iPad Air lag like crazy if i'm drawing a lot on it?
Please help me decide whether to spend more on the Pro or whether an Air will suffice.
Also, feel free to recommend any iPad apps that may be nice for drawing.
Thank you!

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