*DB Pec-Fly is old school and should be avoided because it is dangerous!
*the DB weight distribution is opposite of the loading and unloading phases of the exercise: when the DBs are at the top, above your chest, the chest & front shoulder muscles are fully contracted & the shoulder joints are most
stable BUT there is no resistant other than gravity. This is when the weight is the lightest! When the DBs are wide apart going down toward the ground, the chest & shoulder muscles are stretched & the shoulder joints are least stable BUT this is where there is most resistant! This is when the weight is the heaviest!
*it should be the opposite: when your chest
& shoulder muscles are fully contracted & your shoulder joints are most stable, this is when you should have the most resistant, the heaviest weight; and when your chest & shoulder muscles are stretched and your shoulder joints are least stable, this is when you should have the least amount of resistant, the lightest weight.
*a cable pec fly is better because of the above mentioned reasons! And you could do this standing up, lying down and everything in between.