It's not as firm as leather, but it still has excellent bevel definition. When wrapped correctly, it leaves a small valley at the overlap. The distance between valleys is the perfect width to overlap an overgrip such that it lays perfectly flat.
So if you are a fan of no raised overlap, give it a go! I use Tourna XL, and Tourna Mega Tac XL and both are perfect fits. Here is some pics of the Mega Tac I just put on. My first time with the black Mega Tac which is more of a graphite grey colour.
babolat skin feel. it is thinner than most. it is also firm and is the closes synthetic to leather. I always use an overgrip and the skin feel grip last forever for me. I've used 1 skin feel grip on each of my 2 rackets for over a year and still looks and feels like new.
I was liking Wilson Cushion Air Perforated, but I found Pacific Master's Grip. The Master's is a little softer and a little tackier. Both are about 1.8mm thickness. I don't use over grips anymore. I hate them.
Leather all the way. I've relatively recently started putting leather grips on all my racquets. I've only had access to Babolat, Wilson, and Head so far, but my favorite has been Head.
For non-leather, my favorite so far has been the Gamma Hi-Tech which was already mentioned.