I think poly are a little bit cheaper. I bought two in my early days, when a large national supplier started selling them. Hate them. Just prefer the aesthetics of wood. I know research shows difference in performance, but I notice little between the two types. I also enjoy constructing the flat packs, which I now get at greatly reduced price in the January sales. Even though they are seconds, they go together true and square. Out of 8 boxes I just made up, I had to use filler on two, for cosmetic rather than functional reasons
Whereas I don't hate them, since I have loads of them, I do still prefer Cedar and I think I'll stick with Cedar for any future purchase other than nucs.
Like drex, I've seen no noticeable difference between them where the bees are concerned, but there does however seem to be some compromise or other with the polys, to the point that any benefit is outweighed by hassle.
My preferred set up is now Cedar hive parts with an abelo poly roof. Aesthetically, it's a nice design, fits snuggly and it provides all the insulation the bees will ever need.
When it comes to equipment (hive parts) think twice what is currently occupied, because you will need it during swarm prevention.