You can measure customer facing defects.

Also, lines of code is not completely meaningless metric. What one should measure is lines of code that is not verified by compiler. E.g., in C++ you cannot have unbalanced brackets or use incorrectly typed value, but you still may have off-by-one error.

Given all that, you can measure customer facing defect density and compare different tools, whether they are programming languages, IDEs or LLM-supported workflow.

> Also, lines of code is not completely meaningless metric.

Comparing lines of code can be meaningful, mostly if you can keep a lot of other things constant, like coding style, developer experience, domain, tech stack. There are many style differences between LLM and human generated code, so that I expect 1000 lines of LLM code do a lot less than 1000 lines of human code, even in the exact same codebase.