Battery replacement for Macbook Air 2015 or screen replacement for Macbook Air 2020?

I currently use a Macbook Air 2020 model, having relied greatly on my old 2015 model for five years.

However, I have two main issues with the 2020 - first off is that the fan is incredibly noisy, and often stays on for prolonged periods of time which can be distracting when working. Secondly, the screen likely needs replacement- I'm unsure what has caused the issue, but there are black marks along the top and side of the screen, almost as if a felt tip pen has running out of ink has scribbled on it (see photo). It isn't a major problem, but I'd obviously prefer not to have the marks permanently on the screen.

On the other hand, I do still have my 2015 Macbook Air and generally, I prefer it to the 2020 model - the fan was never loud and I like the overall appearance and feel a little more than my current 2020. But, the battery has completely gone, requiring that it be constantly on charge. Given the magnetic connector which easily is knocked out, it isn't practical as the second the charger comes out the Mac switches off.

I am weighing up the cost/benefits of replacing the 2015 battery and going back to using that model as my main laptop or fixing the screen for the 2020 model.

Given the fixes for either issue are costly, I wonder what others would suggest doing?

The main things I use a laptop for are: Microsoft products for work, general research/internet browsing, some TV/film streaming, and storing photos.

Any guidance would be greatly appreciated!