ipad

You can directly compare models of iPad here:

iPad - Compare Models - Apple

In brief, the current iPad8 is the entry-level iPad - whereas the iPad Pro models are the “flagship” most advanced models, with the most advanced features and a price-tag to match.

The 2020 iPad Air is a cheaper but high-performance model that sits between the iPad8 and Pro models. The Air currently has the most recent generation of CPU, but lacks the most advanced sensors, screen, camera array and adaptive speaker array of the Pro models.

The iPad mini5 is a small form-factor device with a small screen.

Which iPad is best for you only you can decide - which will be influenced by both your needs and budget. Be mindful of choosing an iPad with adequate storage; buy as much storage as you can afford. iPad hardware cannot be extended or updated - whatever you choose is with the iPad for its entire life.

Also be mindful of choosing a WiFi Only model in preference to WiFi+Cellular. WiFi Only models do not have any GPS capabilities, which can limit usefulness if you require accurate determination of location (e.g., using mapping Apps). WiFi+Cellular models include GPS - but do not commit you to using Cellular connections. Cellular capabilities add flexibility is you ever need an internet connection whilst away from WiFi.

First thing you need to ask yourself is what you are expecting to do with an iPad?

All current iPad models all run the same full iPadOS.

All current iPad models all either use the original, 1st or newer 2nd gen Apple Pencil.

( iPad 8th gen and iPad Mini 5 all use the original, 1st gen Apple Pencil )

( 2018 and 2020 iPad Pro and 2020 iPad Air 4 models use the 2nd gen Apple Pencil )

So, iPads are more like cars, now.

You are paying for iPad optional features, now.

Do you want/need larger internal data storage space for data, like music. movies and photos/images and room for other types of data?

Do you need a larger or smaller iPad screen?

Do you need/want an iPad model in a variety of colors?

Do you want/need a bonded, laminated display?

Do you/want/need higher color gamut display with Tru-tone room brightness calibration?

Do you want/need faster, more powerful internal CPU?

Do you want/need more internal processing RAM?

Do you want/need better iPad cameras?

Do you want/need better/more iPad speakers?

Do you want/need the improved, 2nd gen Apple Pencil?

Do you want/need to have the new Magic Keyboard portfolio for the 2018/2020 iPad Pro/iPad Air 4 models?

All of these options are what you need to decide if you really need, or not, and to decide to pay for accordingly.

The more iPad features you decide you need, the more you pay.

It all comes down to how much money you are willing to spend on iPads with additional, premium features.

You can now pretty much do everything on any current iPad model, now.

All current iPad models are sufficiently powerful enough to do pretty much any task put to them now.

iPad - Compare Models - Apple

Best of Luck to You!

Speaking personally, I wouldn’t consider anything less than 128GB as adequate storage - favouring 256/512GB - but my own needs likely differ from your own.

Consider that your iPad is going to have a useful life, in active support, of 4-6 years - during which your needs may evolve over time. The iPad8, whilst a very capable (if basic) device, may not meet your performance needs over time.