This is a common question. The answer has mostly to do with the depth that you are intending to fill or create.
The key differences are:
UVPoxy is usually used as a surface coating for depths up to 1/8” but can be used for up to ¼” depth if you keep the ambient room temperature cool, e.g. 65 – 70 degrees Fahrenheit, and/or position a fan onto the surface to slow the thermal reaction and thus increase the potential hardness of the cure. UVPoxy will generally not cure to a hard surface if it is more than ¼” in depth.
If your pour is deeper than ¼”, we recommend Liquid Plastic.
Liquid Plastic is an ideal choice for pours that are thicker than 1/4 inch and is commonly used for river tables, strengthening cracked wood, encasement and deeper pours. The 2:1 kit provides a hard finish for woodworking applications, but can also bond with stone, metal, concrete, ceramics and other materials.
Another consideration is the cure time. UVPoxy has a 24-hour cure time, whereas Liquid Plastic is a 72-hour cure time.