So I now have the 5mm, 8mm, and 11mm NEO hoods. I ordered the 11mm while waiting for the backordered 8mm because the water was getting cold, and after being spoiled by the 5mm NEO, my Waterprooff 10/5 with bib was no longer cutting it for me.
For some context, it gets down to and stays around 39° (4C) here in winter/spring, and I'll be damned if that's going to stop me diving. I had been diving the Waterproof but found it flushes quite a bit, but still, it was the warmest hood I'd ever had, so I thought it was as good as it got. I also have a custom 12/3 hood from Otter Bay that never worked well for me.
I have been loving the 11mm NEO this winter. No bib, and it's still it's much warmer than my old Waterproof. A lot of that is fit, sure, but I think the quality of neoprene and of the hood in general help. When I finally got the 8mm, I took it to Monterey for some ~50° (10C) water, and it was great at those temps. Admittedly, I was missing the 11mm a little at depth. It's so warm! Amazing hoods all around.