Transformer-based UPS system , are the typical power supply technology for 100 kVA and above and the choice to achieve large kW sizes or provide redundancy.  It's the popular choice in industrial application. The machine has an isolated DC function to further protect the safety of the load. This transformer can effectively isolate the DC component of the inverter output from the load to better protect the load, especially for switches and inductive loads.Therefore, the transformer-based UPS has the advantages of stability, reliability, strong overload capacity, and impact resistance compared to the transformerless ones. Also the transformer-based design allows the UPS to be installed in harsher operating environments relative to transformerless units.

In the financial, transportation industry ,data center construction, general process control (industrial )application such as steel,oil, metal industry when the reliability and stability requirements are higher, it is recommended to use a transformer-based UPS system. 

kstar transformer-based UPS installed in banking data cetner

Transformer-less UPS system or transform-free UPS uses insulated gate bipolar transistors (IGBTs) instead of the big, noisy, and expensive transformer component to handle high voltages.It has smaller size, less weight which can be flexible installedand and transported thus reducing investment and running costs. Due to the IGBT technology, these UPS has high efficecy up to 90-96%, making it more environment friendly. However, IGBTs has lower impact resistance thus it's suit for the scenarios where power quality requirements are not so high such as IT industry and small data center. Also it is the main choice for smallest ratings up to 120 kVA applications  in order to avoid the excessive supply of power while maintaining operating efficiency. 

If you have size&price limitation, Transformer-less UPS system may be a better choice.