How to find the perfect perch.
Why is it so hard to find the correct saddle for you? It's simply because we look by trial and error. Looking for saddles that look comfy or feel good on your fingers. But you don't sit on your hands.
Saddles are design with various elements of the body taken into account. Once you understand how you work with a saddle, finding the perfect one for you becomes much simpler. Yes there is still a bit of trial and error, and that is were a well stocked LBS where you can trial seats becomes invaluable, but you can also be fairly sure that once you know the style and size you need, selecting a saddle will become more simple.
So what are we looking for?
Width. This is the obvious one and something most have thought of. This is based on your sit bone width, not the size of you bottom. A skinny person can have fairly wide sit bones and larger person can have narrow sit bones, so don't assume, check. There are multiple ways to measure this and it is by far the easiest measurement to come by.
Your anatomy is next. How does your pelvis sit naturally? This is very important and a bit more difficult to assess and understand. It dictates the shape of the top surface of the saddle. Flat, neutral (slight contour on the upper surface) or wave are the 3 most common shapes. This will be determined by your natural pelvis position and quite common determine if the saddle is comfortable on a very short sit. It is very obvious if you have the wrong width or shaped saddle.
The last step of measurement is your flexibility and the dynamic movement of your pelvis. This dictates what type of cut out or groove you would benefit from. Quite often this is the cause of numbness on longer rides. Getting adequate support but the correct amount of relief is an important part of the puzzle. Most people with benefit from some cut out or relief groove.
Finally, personal preference. Some people like a firm seat and others like a soft topper. This is sometimes depends on the period of time you spend on the bike but only you can know what you like. Having a saddle fit by someone competent will give you the correct size and shape. All you then have to decide is what topper works for you. Don't just look for well padded, most will benefit from something in the middle ground.
So the simple answer to the question is that saddles aren't simple. There is a lot to think about.