Is it worth it? Depends. Others have said, resolution difference on an iPad maybe noticeable but it's going to be relatively minimal. Where the most notable difference is going to be is in the the HDR implementation. Most iPads can't properly do HDR right now. I am not sure of the specs of your devices, but accepting and being able to process HDR is TOTALLY different than being able to properly display it. They can probably accept it, but the contrast ratio may or may not be up to par. I know the iPhone 11 Pro has a higher peak brightness capability so it is able to better display HDR content. The Pro XDR screen coming on the 12.9 iPad Pro theoretically will be the most capable of all the consumer-available devices, at least that Apple makes. Because of the capabilities of that screen, 1,000,000:1 contrast ratio; the peak brightness capabilities of 1600nits, covering the full P3 color gamut, it should be able to very properly display HDR. Truthfully those numbers rival some of the best 4K/HDR TV capabilities even.
600nits that's on the current iPad Pros are nothing to sneeze at either, however, the contrast ratio is somewhat sub-par. There's a difference with raised blacks and having 600nits peak brightness (that the current ipads are capable of) versus having proper blacks and 600nits, (ie LG OLED TVs).