Plenty of options for this one. All of the following can be made to sound snarky if said with a sarcastic tone, but none of them carry an inherent negative connotation.
It's up to you. OR I'll leave it up to you.
It's your call.
I'll let you decide.
Let me know what you prefer.
It's up to your discretion.
You're free to choose.
The choice between these depends a little bit on context. If you're trying to convey that you want them to choose, but that you don't need a say in the choice, I'd personally choose "Let me know what you prefer," because I want to stay in the loop.
If, on the other hand, I'm trying to say "I don't care what you do" in a polite way (simply saying that I'm not affected by the choice), I'd lean toward "It's up to you."
Again, it depends on the situation, so when deciding which to use, it's up to you. ;)