In the situation you're describing, we couldn't chose, we regularly do both and both are sooo exciting in their own ways :)

I love masturbating in front of my partner, even more so when they just stand in the room naked, maybe thinking of what to wear, that is just perfect inspiration

Interesting question. I think I'd find someone watching me so closely while I am pleasured or reach orgasm the hottest part of this situation. I think I'd choose to play with myself, because I think could do that with minimal attention and maximize mutual focus on the watching/ being watched. hbu?

I'm sure I'm not alone in this, but my kink is deep affection, and so I love so much more to be touched than to touch myself. I could probably get close to an orgasm just from someone softly stroking my hair... so if I were to have an arm around my neck pulling me close, and the other slipping down below the belly button? Bliss.

Masturbation, even mutual masturbation watching each other, just isn't as good.