Epoxy is a thermosetting polymer which is available in three different formulations: water based, solvent based, and 100% solids. These formulations allow for varying degrees of thickness from 3 mils to over 10 mils for a single coating. Epoxy is easy to apply, has special bonding characteristics, and has low VOC. Epoxy bonds extremely well to properly prepared concrete and can sometimes be used as a resurfacing agent for old or worn concrete.
The best epoxy formulations are 100% solids and provide for an extremely hard, thick, and impact resistant surface. This self-leveling thickness contributes to filling in the small hairline cracks and imperfections of the floor as well as providing protection. It also works well against hot tire pick up, scratching, and wear from abrasion. Though some epoxy formulas come with U.V. inhibitors, they will still eventually yellow or amber when exposed to sunlight for any length of time.
Something else to consider is that most epoxy clear coats are not actually crystal clear. Though they have no color, there is a slight yellowish brown tint to the clear epoxy formula.