OVERBUST OR UNDERBUST?

Overbusts and underbusts serve the same function in terms of waist enhancement and back support. The most obvious difference is the overbust corset covers the bust and offers more coverage. Overbusts are fantastic for outerwear, underwear, formal wear and lingerie. Underbust corsets offer the same benefits but tend to be more versatile and practical for purposes of waist training, frequent wear or daily wear. Overbusts can serve the same purpose, but can be more restrictive for the new corset wearer.

CHOOSING LENGTH

Once you have decided on either an overbust or underbust, the next decision would be selecting the proper length corset. This should not be based on your height. This should be based on your torso length. 
It's important to pay close attention to the corset front lengths stated in the product descriptions (shown to the right of corset image). Compare these lengths against your own torso to ensure the corset will not be too short (allowing soft tissue to squeeze out the bottom) or too long (preventing the wearer from sitting comfortably). You can take a vertical measurement of your torso while sitting completely upright in a chair - starting at the center underbust at bra strap (for an underbust style), or center bust at nipple line (for an overbust style). Next, pull measuring tape downward to the length stated in the product description. This will give one a general idea if the particular style will be too long or short.