I just had to make a similar decision!
Mirage of Blaze (yes, Rilezu cels - stop yer moaning)
It came down to two: both were beautiful, and both were from a great moment in the show and both were the same price. But one was more "moment" (where Takaya comes alive in Naoe's arms, Naoe is crying), and the other was more "eye candy" (where Naoe has Takaya in his arms in the boat, just after he has revealed his plan for eternal bliss, but is interrupted and so is looking up. The angle and colors are great, his eyes are lovely).
I agonized for 24 hours (hey, it was a looooong 24 hours for me), and finally came up with the eye candy. My reasoning: if I wanted the moment, I could just pop in the DVD. But the eye candy freezes a perfect moment of beauty without burning a hole in the DVD.
So there you go. I voted beauty. Everyone else but me probably could have guessed what I would choose.
