What makes for the best mate? Well, that’s all dependent on what is needed. You wouldn’t use a Concentric mate with an arc/circle and a line, would you? No, because that wouldn’t be the best mate. The best way to understand mates is to work with them. You want to use as few mates as possible, while still locking in the part you wish to lock in using a mate.
Concentric Mate and the Coincidence Mate
The two most commonly used are the Concentric mate and the Coincidence Mate. These are popular, because they create a good foundation to locating your components quickly, oftentimes with very few additional mates. Using these as a base for the other mates to be used off is another reason they are most often used. For instance, mating a Screw would require a Concentric mate along the face of the Cylinder for the screw and the face of the hole. Then, you would add a Coincidence mate to the face on the bottom of the screw head to the face the hole lies on. This would easily locate the Screw into the Hole. If you wanted the part to be stationary and not rotate within the hole you would use a Lock mate. So, as you can see, you typically use these mates at the start of the Mate addition process. The different types of Standard Mates can be found here.
The order with which you place your mates can also be important. Going back to the screw and hole option. We can reason that, using the Concentric mate first would be the best first step. This will align the cylinder to the hole it will need to use. Placing the Coincident mate first may cause the part to flip or rotate thus making more actions to flip the part and orient it correctly. Why go through the extra work, when you can reason which mate will work best prior to employing the command?
Once we have the basics handled, we can get into the more advanced mates which have their own uses and situations. Advanced mates would be used on a case by case basis, the options with Advanced mates are available here.
Advanced mates are great for allowing the movement of paths, i.e. Milling. You can use the Path Mate to designate the path it can move along for visual purposes or Collision detection. Another popular mate in the Advanced category is the Limit Angle. This mate allows you to move within the range of a specified angle. Advanced mates are great because they give you a bit more range of motion and options that the Standard Mates.
Mechanical mates also give more range of motion while limiting it at the same time. They also have a bit more to know behind them. Mechanical mates are more designed to better display motion or specific functions. From CAM to Slot, Mechanical mates has more to offer for better ability to simulate the motions you are looking for. A list of available Mechanical Mates is available here.
Flexible Sub Assemblies
Now that we know about the mates, how do I keep from having a bunch of mates in my assembly? Flexible Sub assemblies! Flexible Sub assemblies can be helpful because they can allow for motion in certain parts of the Assembly without the need to have a bunch of Top-Level mates that can cause problems if the mates don’t play nice with one another. A Flexible assembly will allow the movement without the added addition of mates which means there is less chance for error. Information on Flexible Sub assemblies is available here.