An optimized fine grained payload with compression can out perform the course approach. Course payloads have added cost to swap in the DOM, and fine grained payloads don't require complex architecture.

Asides from rendering I have additional concerns about course SSE payloads. You basically remove any cache capabilities (though this is common with all update streaming approaches). Uncompressed the payloads are quite large and the browser may not be able to dispose of that memory, for example Response objects need to hold all body data in memory for the lifetime of the Response because it has various methods to return the whole body as combined views of the buffer. Also benefits of compression for SSE payloads are going to be drastically reduced in situations where connections easily get dropped.