Find the one who takes the most conservative non-surgical approach to treatment - if they immediately pressure you to do any type of invasive procedures and try and frighten you (eg, if you don't do this all your teeth will fall out) or guilt you (eg you owe it to yourself or you will only have yourself to blame if you don't this) to into doing something you feel may be unnecessary then find another dr. A good perio will advise what he sees, his recommendations and will let you decide one way or another and comply with your wishes. He should also welcome that you seek a 2nd opinion. If he withholds some treatment unless you do all of what he recommends (says we either do it all or nothing) then I would find another dr.