All nail polishes are not created equally. Clear nail polish is still just nail polish--vulnerable to chips and peeling, but a top coat will protect your nail colour against scratches, chips and other annoying dings because it dries harder.
A base coat is a clear polish that goes underneath nail polish, and it can contain proteins, vitamin E, calcium, aloe vera and other ingredients to promote healthy nails. Nail polish is either clear or a colour and goes on after the base coat. A top coat is the last step, which is designed to make nails harder and keep them looking shiny.
Unlike clear nail polish, top coats are designed to dry hard, so they are less susceptible to nicks and scratches. Top coats also have quick-drying properties, so you can apply them over nails that are nearly dry and they will dry faster.
A top coat will extend the life of your manicure, which usually last about two weeks. A top coat can be reapplied five to seven days after your manicure and then as needed.
A top coat can be worn alone, however, that is not its purpose. It would be better to apply a clear polish and then the topcoat for optimum results. Ideally, a base coat should be used as well to keep the nails healthy.
Nail polish works best when you use a base coat, polish and then a top coat. This way the colour (clear or otherwise) is sandwiched between two protective layers. Skipping a step will sacrifice nail health and manicure life.
When used in combination with a base coat and colour, your nails will be protected from yellowing, colour will go on smoother, nail defects--such as scratches or lines--will disappear, and chips, peeling and cracks will be less likely to occur. Try using a nail buffer before your manicure to buff out nail defects.