And timber look is PVC, polystyrene, polymer? Who knows what the difference is, but you can be sure there are differences and they relate to stability and longevity of the blades under extremes of UV exposure, heat and humidity.
There were failures in the early days of the timber look product in the Queensland environment. I believe the mainstream window furnishings industry has settled with proven product now, and innovation in fashion will lead the way.
The majority of timber look Venetians are sold in white and neutral colours, but the simulation of timber stained finishes has improved immensely. Where does that leave actual timber blinds? The cheap ones in ready painted and stained finishes in basswood and ramin etc are inexpensive but with coated finishes they will not handle severe sun conditions as well as the synthetic equivalents.
As far as the long established cedar Venetians go, the same applies. The painted or stained finish is the weak link, not the timber which is as stable and long lasting as it is beautiful in grain and texture. For cedar blinds, and this applies for shutters as well, do not expose them to severe sun conditions, or else go for an oiled finish which has to be regularly reapplied.