You seem to be looking at two fairly different jackets since one is a 2.5 layer and the other is a 3 layer. A 3 layer jacket has 3 layers in the shell (nylon, membrane, inner material) where as a 2.5L jacket is made lighter by just using nylon, membrane and then the '0.5 layer' which is usually some sort of a printed pattern. I'm a little fuzzy on the purpose of this 0.5 layer, but I think it has something to do with protecting the membrane and maybe raising it off the skin slightly.
The 2.5L jacket is going to be lighter and in my experience a lot more comfortable in warm, high exertion applications because a 3 layer jacket is typically more insulating. Durable winter shells are normally 3 layer whereas lighter summer jackets are 2.5 layer if you are looking at good ones. Cheaper jackets will be 2 layer but that's not as good as 2.5 layer because a 2 layer jacket is nylon, membrane and then they normally hang a mesh liner in the jacket, so it really is 3 layers but the 3 layer isn't attached to the others. 2 layer jackets are cheaper to make.
First I would decide if you want a 2.5 or 3 layer jacket before you decide on the membrane. A 3 layer jacket is typically going to be a more durable jacket because it's usually designed for more abusive winter conditions so they use a heavier grade of nylon for the shell. There's lots of 2.5 layer jackets that are plenty durable though and I prefer these over a 3 layer since they are normally not as hot to wear (insulating). I find that 3rd layer of material (the name eludes me) adds a fair bit of warmth which isn't what you want in the summer.