Having always wanted to wear the thinnest suit possible, I have preferred a 5/3 for winter use for many years. Last winter I decided to go 6/5/4 Guru+ Hood and just be as warm as possible.
The Guru range is the top of the line performance suits from Sooruz. It features all their latest tech including the latest version of their Oysterprene. This is a form of neoprene developed by Sooruz which uses crushed oyster shells to create the foam. The seams are all glued and stitched (GBS).
The Guru+ features the most of the fleece lining - all the way down to your ankles. This is made of recycled polyester and nylon and keeps you really warm whilst also drying quickly.
Now well into my second winter in this suit, I cannot imagine using anything else. In the coldest of days I have been pretty comfortable. Regularly sup surfing with no gloves watching other water users hide their hands under their arms. Kite surfing for the most part with no gloves either. On the coldest days a pair of Open palm mitts protect the backs of my hands from the wind chill.
Any concerns about freedom of movement or bulkiness are long gone. The warmth is worth it. In terms of durability my suit is holding up really well and has no issues. I am not the toughest on my gear, but as mentioned already, well into 2 seasons it is now showing any issues.
I have mentioned how well it performs on the colder days. On the warmer days, doing activities that generate more body heat like sup surfing, I have definitely been very warm. However the water is still very cold, and a quick dunk soon has your temperature back down. It is much easier to cool down on a warm winters day, than it is to warm up on a cold day. I cannot see me not having a 6mm hooded suit like this again.