The Difference Between Bumper Plates
Black Economy Bumper Plates
The pics above I got from the Rep Fitness bumper plate page (good prices there too). These plates will always be the cheapest, and the most common at many gyms. They have low bounce, are relatively thick, and are fittest with small steel inserts. These are great for CrossFit workouts, home gyms, and commercial gyms on a budget. For home use, they will last many years and are likely never going to need to be replaced.
Some things to look for in quality black plates are inserts that have some method of attachment beyond just being pressed in. The better plates will have hooks to help secure the weight, and also be inset/recessed so that the insert doesn’t hit other inserts when plates are loaded on the bar next to each other.
Color Economy Bumper Plates
Color econ plates are basically the same as the black econ plates with the addition of a layer or two of color rubber. This adds a little bit of durability, and adds the benefit of being able to quickly identify the weight of plates at a glance.
Competition Bumper Plates
Competition bumper plates are designed for Olympic weight lifting. They typically have very strict weight tolerances (+/- 10 grams versus +/- 2% for econ) and are designed with large steel discs in the middle to help with that. They are also typically more durable as long as at least 1 20kg disc is on the bar.