Firefox - By far the best. Quick response, usually from engineers. If it's important the fix will be quick.
Edge - No reply for months / years. When I've gotten replies back it's been to ask me to try with the current version. When I do and the bug still exists it goes back at the bottom of the queue it seems.
Chrome - Somewhat of a mixed bag. Some times responses are quick, some times they are from engineers. But most often I get replies that convey the person I'm speaking too is a very green QA type. I've gotten replies that the test case I provided them doesn't reproduce the bug, because they had attempted loading it with the file:// protocol (of course hardly anything works with the file protocol). I'm not sure, do they expect me to include a web server for them?
Safari - Only tried a couple of times, never gotten a whisper back.
I would rate my experiences as:
Firefox - A+
Chrome - C
Edge - D
Safari - F