Since launch, I have been using "Locale Only" for search preferences (matchmaking) and realized today that default was a better option for me.
Locale Only - I tend to get more 3 bar connections and the regional matchmaking isn't working as I'm getting Australian Host/Players more often.
Default (from today) - 3 bar connections, few four bar connections but better hit detection, less bullet lag etc. Also getting New Zealand players rather than Australian Players.
Does the default setting look at your connection which then selects a lobby where players have similar connections to you? (Ping?)
Is Locale matchmaking a broken matchmaking system since it's not looking for players closer in my area (I'm getting more players from a different country)?