If bug count is proportional to LOC and LOC per day are constant across languages, then bugs per day might be the same. But you'd still expect features to be getting implemented at a higher rate, and you'd expect a lower bug count per feature. That's ultimately the metric that's most interesting from a business perspective.

IME, the bugs are also easier to deal with in the more expressive language. They tend to be things like faults in the business logic or gross edge cases that people are likely to catch in code review or QA. Whereas the bugs in languages like Java seem to typically be really annoying things like off-by-one errors, comparing Integers with ==, and goofy run-time type errors that sail past the compiler because of weak static type checking when generics are at play, and also past code review because people aren't expecting to have to review for type errors when they're using a static language.