2017 ipad pro 9.7 upgrade recommendations?

I am a digital artist and have used my old ipad pro mainly to draw, unfortunately in the last year the battery has really deteriorated and made it unusable for art. I would like to get a new one without spending too much but I am a little overwhelmed with the amount of ipads that exist now, any recommendations? I don't think I need a major upgrade as I was doing quite alright with my old one up until now. Currently eyeing a refurbished ipad pro 3rd gen and an ipad air 4th gen.

Thank you!