Thanks for the replies everyone!
All I use are poly hives from Lyson. Lots of varied opinions about them.
You could write a series of columns of pros and cons....in my opinion mostly pros.
My thoughts are that any insects that need to regulate the temperature inside their "home" need all the help they can get to maintain it.
Well what are they? I'd like to hear more.
Well you did ask
Pros and cons?.a big one that has had a lot of debate (heated at times) in the UK.
I think whether poly hives give you an advantage or are beneficial to the bees will depend a bit on your climate. Perhaps fewer advantages in warmer climates and more advantages in cooler climates
Logically, to me at least, any insect that needs to regulate their internal cavity temperature will benefit from any help they can get in stopping heat loss. That's not to say that wood is bad but poly is more thermally efficient.
This is certainly noticeable in over-wintering where bees will survive in either wood or poly but consume far less stores over the same period in a poly hive i.e they need less energy to survive the same conditions.
Where I see a difference is in the spring built up. Our springs can be quite variable and often we can have a couple of abnormal cold months and here I notice it has little effect on the bees progression in poly hives. A comparison of numbers of brood frames between wood and poly has shown that usually there are 2 or more frames of brood in poly. Note I say usually with bees there are always exceptions! But usually this means more bees when our spring/early summer nectar flows start. It's no co-incidence that one of the largest commercial beekeepers in the UK is moving over to poly hives as he estimates his honey yields are up by approx 1/3 compared to his bees in the same apiaries in wooden hives.
Sorry this beginning to look like a long diatribes, so I'll try and cut it short.
They are cheaper than wood (approx 50% cheaper in the UK). Of course it's easy to make your own wooden hives rather than make your own moulded poly ones.
When you drop a poly box it cracks open along a defined seam and is easily repaired, whereas drop a wooden box it tends to split and usually become irreparable. Although not sure dropping of boxes would be a good reason for using poly.
Poly rarely distorts over time, some of my oldest poly hives are 15+ years and still going strong.
Also much lighter than wood, a concern as I age?..
One disadvantage of the Lyson poly hives is they have hard plastic edges which gives them longevity but can create a problem with water ingress if the two touching surfaces are not cleaned, You can get little ridges of propolis etc that act as small gaps between the two edges allowing water into the hive in very rainy conditions. Easily solved by scraping clean both edges or coating the edges with a little Vaseline (grease).
Many of the pro-wooden hive proponents in the UK say they see no benefits in poly hives vs their wooden hives. Which, for many UK beekeepers, is probably true. But I think the main reason they see no difference is because there is a stubbornness within the UK beekeeping community that insists on keeping local mongrel bees as opposed to strains that have been bred for fecund queens and honey production. If you put scrub cattle on grade A grazing you still have scrub cattle at the end on the day?..put a pedigree on good grazing and you would be amazed.