The simplicity of setting up basic calculations

Best thing about PLECS is therm modelling allowing you to get a good approximation to real results and different operation points.

Simple drag and drop blocks, all components are idealised, and basic loss parameters can be inserted. Else, you can build your circuit/system models by manual adding discrete components to simulate your parasitic elements, ensuring that you are defining every part of your simulation in as much detail as you require. This makes PLECS far quicker to get results than a traditional SPICE simulator if you are not concerned with device-physical behaviours. The software also features the ability to quickly and intuitive build sub-systems within your simulations by masking a prebuilt circuit create a functional block - for example, you may model a multilevel converter, but have it masked under a sub-system block with only the gate signals and power inputs/output available in the main simulation. This keeps your working area nice and tidy and also means you can easily reuse circuit elements across simulations. The software also possess the ability to do simple thermal analysis by use of thermal resistance/capacitance analogies. By no means as effective as FEA for thermal analysis, but a good starting point for early systems development. There are also mechanical domain simulation elements included, but I have not tired those in my line of work.