HR display on watch and HR straps

Hello,

simple question : when i have an HR strap, connected to my Garmin obviously, is the HR displayed on my Garmin/on garmin connect the one from the strap or the one from the watch ?

Because i bought the strap after reading it was much more accurate than the watch one, but despite seeing that my watch is connected to the strap, i never see any difference so i am wondering.