I was told that the lighter the gauge string the more likely you are of having fret buzz. I have considered going from medium to something a little lighter. Wouldn't a simple neck adjustment take care of any problem?
A lighter-gauge string will have less tension than a heavier-gauge string tuned the same, so there is more potential for lighter-gauge strings to hit the frets when struck because they are a little looser. It really depends on your attack. If your attack causes the string to hit the frets, you could adjust your technique or raise the action a little.