Why would you want to change to best connection available?
when you go to the Multiplayer Menu, then Public Match. There is a option at the bottom of that screen, "Search Preferences"
set it to best. yes you might have to wait a minute or so longer to get into a match, but if you get into a good lobby with a great connection, you'll be happy you waited.
People are complaining about the hit markers, but i think a lot of that stems from this game taking more bullets to kill an enemy than in the past. In BLOPS if you were on a shite connection or bad host you could put endless amount of bullets into an enemy and them not die.