You don't need to choose one or the other.
BitChat for everyone who has the phone (so basically everyone). Than you can use Bitchat-meshcore bridge - and you need just two - to connect those two meshes. Not perfect, it only interconnects the channel data (very hard to do full bitchat protocol bridge over lora), but this combines advantages of both - range of meshcore, no hw requirements of bitchat.
https://github.com/jooray/MeshCore-BitChatAnd your point is exactly right - hard to setup when you're being bombed. But it's easier to connect a few areas with a few devices and then use bitchat in populated areas in the local mesh.