Quinn Vs Vayne
Who do you think will win on a 1 v 1 quinn vs vayne?
vs 
Who do you think will win on a 1 v 1 quinn vs vayne?
vs 
define "win"
I'd go with Quinn.
Quinn wins because Vayne mains will get impatient after a few seconds and die on a bad tower dive.
id say
because of the blind...
If Quinn hits her blind when Vayne ults Quinn wins. If Vayne dodges the blind, and lands condemn against a wall, Vayne wins. If condemn doesn't hit a wall, it's Quinn's favour but still could go either way depending on builds.
This all assumes they're equally levelled and itemized. If it's a Quinn top v Vayne ADC, Quinn's level advantage will often mean she wins.
Vayne because you can't even counter the fact that you don't see her during the entire fight while she instantly melts ur health down. Quinn's blind is , in fact, easily dodged. However, maybe Quinn would win because she can reveal Vayne!
Skill matchup.
Both of them rely on certain skill shots (Quin blind, Vayne condemn) to win duels. If either of them land it and the other doesnt, they win. If they both land or both miss, Quinn has the upper hand because she has more burst damage to nuke Vayne with.
Who do you think will win on a 1 v 1 quinn vs vayne?
Generally it would be whoever shoots first.
Both deal a ton of damage and are made of tissue paper. If you have the drop on another marksman with either, that poor shmuck is already at half health by the time they can react.
In the case of both smacking one-another at the same time Western Duel style, I'd probably give that to Vayne. Vayne's tumble gives her a pretty good chance to dodge Quinn's blind if she sees it comming, Quinn is 100% dead if she gets Condemned into a wall, and Vayne's Final Hour stealth will set the duel's tempo to match Vayne's rythem.
Shauna Vayne
I wonder if you can tell Quinn apart from Vayne if she wears Vayne's dragon slayer outfit?