Yeah, Frink is a Turing-complete programming language. That's a provably huge difference. You can have loops, maintain state, store results in variables and use them later, and define your own functions, so your calculations are repeatable and can be more than one line. Can't do those things with Wolfram Alpha. Frink has an unambiguous, documented syntax, rather than a bunch of tricky and finicky hard-coded rules that try to parse English sentences.

You own the output of your calculations, not Wolfram?

Frink is a general purpose language, not just a unit conversion tool.