I’ve been conflicted about this. For example beehaw has a larger technology community but I’m a fan of lemmy.world so I try to post interesting content there to help the site.
Beehaw might not be the best example since it’s defederated but you get the idea
I mean post it on both. It’s no different than the age old issue on Reddit of having two similar but slightly different tech subreddits where your content would fit on both. That’s what cross posting is for. I’m not sure if you can simply cross post on Lemmy but even if you can’t just post it on each community separately, it doesn’t make any difference.