I was just wondering if there is any difference in playability between slick 6 string and polyester string. :
Yes. of course. I prefer Slick 6 because it is 50% Cotton, 50% Polyester. It is very smooth and durable. Polyester, It tough and nearly un-breakable. It hold up for long combos and works great. Its a little more thicker than Slick 6, while Slick 6 is thinner.
It’s all preference.
I like polyester strings better, but many peple like 50/50s better.
There will be difference in play though, try both to see what you like.
What I notice is that for me, Slick 6 gives you a callus easier because of the cotton rubbing on your skin.
Poly feels different and lasts longer. Also plays really smooth.
There was a thread similar to this yesterday. I think it may contain some useful information for you:
Yeah. Hey, I remember that thread! I was going to say that!
I think ill tryout the polyester, cause Ive been playing with slick 6 for a while and its kinda uncomfortable
Thanks guys 
Sure thing!