Firstly you need to know the core consideration criteria for each item:
For sleeping mats for example, they are: 1. Warmth / R-Value, 2. Dimensions, 3. Comfort, 4. Durability, 5. Weight, 6. Price.
While the consideration criteria for each item are universal, each person's consideration of what is most important is individual.
For example, adequate warmth, then comfort, then dimensions, then durability and then weight are my (Michelle, Byron Hikers Marketing Manager) order of priority of considerations when choosing a sleeping mat. However other people may be more price-conscious, while extreme ultra-lighters will always choose weight first.
The presentation below will take you through how I chose my sleeping mat + the other 4 core items in my multi-day setup. This will help you frame and structure your own decision-making. It also has brand names for you to research + other helpful tips.