The lemmy.ml instance has some controversies regarding its maintainers, which may have an impact on adopters. programming.dev seems safer for now, for programming communities; I just hope that it's a well-maintained instance.
👋 I hope this will take off
I think people fear a problematic "BDFL". On the other hand, the beauty of FOSS is that it can be forked in case you don't agree with the current owners.
I heard that Lemmy is the second most popular software on the Fediverse, and choosing between Lemmy and kbin doesn't have much impact due to the interop (although I hope to see tools for easy migration, if needed). What matters is how well the instance is maintained, and the community.