Based on the title, whats the smoothest yoyo you’ve ever played??
Then is it has a long spin time or not?
For normal production it’d be a radian gen 2 from spyy
For prototypes it’d be the tigorylla from hspin
Also in brand alone anything from s.kon is pretty much guaranteed mind blowingly smooth but you definitely pay the price.
I’ve got 11 yoyo’s ranging from low to top end.
Best out of box- cascade. Vilmos zoltan kiss colorway. Threw it for 5 minutes fresh out of box and I could not tell it was spinning or on the string. Literally the definition of perfectly smooth. Hit it on the wood floor in minute 6 and now it just plays like a typical high end. Very smooth but there is slight vibe. Don’t get me wrong great throw, but I’ve never felt anything like that first 5 minutes, I’d need to come up with a new word to describe how literally perfect the physics on the spin was. Weird feeling but amazing.
Best overall after normal use- Hubstack genesis- black- beat this thing on concrete, wood, acid, shot it…well ok no acid or guns but you get the picture… Still played smooth like a high end throw till I lost it…rest in peace…
rainfly… it was dead smooth.
other then that triton, albatross… oh i forgot the 2hot… that was beyond words.
anything tp or yoyoempire
Irony JPX by a mile
Genyo majesty
The QU4DRO but that was my first full metal yoyo so I don’t have anything to compare it too! XD my next on was the T5 magicyoyo but I saw that the QU4DRO was WAY!!! smoother. 
getting a benchmark we will se what I think of my QU4DRO after I get it! XD
BA Majesty
Pulsar 2014 Genesis. DEAD SMOOTH. MELTED BUTTTTTTER
Other than that, Monsters are really really smooth. The finish makes it feel even better.
I was surprised how smooth my blue john chow edition is because of how you can feel the layers of the splash on it, so smooth.
The smoothest throw Iv’e ever thrown has to be my clairview blizzard canvas or my hot fire lava sasquatch.
Toss up between my Sleipnir and Blink.
The Blink had teflon tape in it from its previous owner, but it was still slightly vibey. I unscrewed it to pick out a huge knot, put it back together, and it was as smooth as my Sleipnir. Hopefully it’ll still be the same way after I get it back from being re-anodized and blasted. 
Equilibrium from Marcus Koh then followed by Berserker SS.
TP paranoid with a nice clean bearing in it… also my SPYY orbitron 5000 is a very smooth yoyo as well
Probably Shipwreck from Tropic Spins.
OD Code 2
I agree on the 2014 Genesis. sooo smooth…
But even smoother is my C3 Krown… It’s just on a level of It’s own.
my smoothest yoyo is TP levi 5