A cursory check reveals some answers:

* the one you linked is a browser-based thin client; this one runs right on the user's machine

* 100% less Docker and other devslop—drastically simpler deployment and development cycles

I think Stirling PDF is a great product, but there meant for more Enterprise level users. LuxPDF is meant for very quick file conversions or modifications and is geared towards freelancers, students, small business etc.