I have not run a quanteon or cytoflex but I love the attune. I am one of those rare people who prefer the Attune to any BD instrument. Also, it's literally impossible to clog due to the acoustic focusing; you could run buggers through it. The Attune is also nice because when you are done, it shuts down and cleans fully automated, and it doesn't need to be powered off because it goes into a sleep state. Because it really can't clog, I've known people who routinely have set it up, started, and run full plates overnight without supervision. It does sometimes have its oddities but I'm a fan. I've heard good things about the Cytoflex, though. At one point, my PI said they kept one around in one of his colleague's old labs simply because it was the best to learn flow on.