The Eddies are mainly true to size for most individuals. and half size up for some (with wide feet, bunion, or just hate having to break a shoe in). It Should feel snug when you first try them on, because the leather is so thin the shoe will REALLY STRETCH OUT after a couple weeks of wear. If you don't plan on wearing them all the time and if you are someone that has a LOT of shoes that you rotate wearing, then it won't be a big deal if you get half a size up since they probably won't stretch that much considering you aren't wearing them all the time.
The sole is thin because that's how the shoe is going to be flexible and comfy. It is cushioned with memory foam and most people feel like they are "walking on clouds" when they wear it.
Lamb Leather in general is going to feel better than the patent leather. But that's not to say that the patent will hurt more. They are both a comfortable shoe and just has a slightly different feel to it. However, INSIDE the shoe, both patent and lamb leather has the same material -- lamb leather. Patent will just be much easier to clean and also water resistant.