Well, I'm a total wimp when it comes to temperature. I had a compressed neoprene dry suit first, and I use the same undergarment (4th Element Halo 3D) as I do with my trilam one. For trilam, I do have some more layers.
One thing to remember, I'm a total wimp when it comes to temperature. So YMMV as compared to mine. I found the neoprene more restrictive overall (I felt like a Michelin Man). However, it did come at a cost.
I am looking at Fortress Clothing for a warm/thin top to wear with my undergarment and heated vest.
Again, I'm an outlier on the extreme end of cold tolerance. I should not be used as a guideline, but a data point. Those with similarly poor cold tolerance, you're not alone!