There isn't "the best" product when it comes to scientific utilities. You can mostly resume to the "one that fulfils my needs". The Refrigeration Utilities already contains one of the best tools for the calculation of thermal, geothermal and cold loads. However, you can try the software from GLD. It's a complex application that is mostly used in the geothermal load and calculation domain and area of work. Access its website to find more information about it.