Of the two, Star Wars Premium is the better choice in a single pin collection. I agree with @frunch, it's easy enough to sell if you don't like it.

Star Wars appeals to a bigger audience, so more potential buyers. Stranger Things is a Netflix series with about 40 million viewers, that is a lot but no where near Star Wars. But if you want the STLE, get that. Pins are a work of art, and if the art/theme speak to you more, you have answered your own question. Code will only continue to get better with Stranger Things too.

With few exceptions (Tron LE is one), used LEs generally are available at a reasonable price (slightly higher or slightly lower than new). And even the Tron LE is available if you are willing to spend $10K.

I have a playfield protector on one game, my Goldeneye, it came that way. Someday I will remove it, fix the magna save wear spot between the flippers and clear it it. Until then, its fine. No plans to put any on my other games, even some with cupped inserts.

I agree with @vireland, clean and wax it with a good carnauba wax (Blitz is the wax of choice for a lot of pinsiders). For how to, reach Vid's thread, cleaning and waxing pinball machines:

https://pinside.com/pinball/forum/topic/cleaning-and-waxing-pinball-machines-vids-guide#post-2655215