BoTW for me. Skyrim was my least favorite of the console Elder Scrolls games, I'd go back and play Morrowind or Oblivion over that, all three of which are completionist nightmares so you'll have fun with any of them.
I can't imagine playing Skyrim in a scenario where you can't mod the ever loving bjesus out of it. If you can't play it on PC, I'd honestly not bother. The story certainly isn't worth it, and vanilla content is mediocre at best.
Both Skyrim and BOTW had me by the nads for months. I am a softy and would opt for Skyrim, since I literally clocked in over 200 hours in that game when it first game out in 2011. Such good memories from that game.