If your going to use them I would stick with the wraps IMO...their by far more stable and you can wrap them nice and tight. As far as use is concerned, I only use them on sets over 500 lbs cause I dont want my knees to get used to relying on them. I wont use them even everyonce in a while just to make sure.
Will the help your knee pain? What I would do us use them for 2-3 mabye even four weeks....then when you go back to squatting without them and you will be able to tell. If your knees hurt more, they didnt help and made them weaker. If they feel better, they helped. Otherwise just use them on your heavy heavy sets.