I don’t mind Mail.app for most uses, it’s nice to have a native mail application. In Gmail, I use shortcuts. These are some of the shortcuts I’ve discovered in Mail.
Cmd+N– Starts a new message
Cmd+Control+N– Starts a new note (like a self-email)
Cmd+R– Replies to a highlighted message
Cmd+Shift+D– Sends a message
Cmd+Shift+N– Refreshes the inboxes
delete– Removes the message from the inbox (but leaves it in All Mail)
These shortcuts aren’t hard to find but unlike Windows, there are more functional keys on the Mac. This means there are more combinations and shortcuts than I would’ve expected. There are of course numerous other shortcuts but they’re a little hard to find in a single location.