My experience of wooden blinds is that they definitely reduce the amount of natural light coming into rooms purely because of their thickness, so if you do decide that they are for you I would opt for the 50mm slats.
Having said that, they are very good at retaining heat in a room compared to any other sort of blind.
Another downside is that, unlike an aluminium blind, if you pull them up they don't go up as far, & just don't look right.
They also don't seem to close as tightly as aluminium blinds, & as far as privacy goes this to me is a disadvantage.
They are also much harder to keep clean, & physically clean than aluminium blinds.
Alu-Wood blinds are what I'd recommend & recently went for, & am really happy with them as I like the wood effect - they are aluminium blinds with a wood effect look. They conquer all of the above mentioned downsides, but of course don't retain inside heat as my old wooden blinds did.
You can get wooden blinds in all different colours now, which is great, but I found that when I was shopping around that they all seemed to be on sale & special offer. Call me cynical, but this actually turned me off & gave me the impression that they were trying to get rid of them instead of how popular they were as manys the salesman tried to convince me!?