IMO, no. The hard strap has been reliable and I am unaware of it within a minute or so of putting it on. The soft strap offers no benefit IMO and there has been some reliability issues related to it's connection the the transmitter module. I believe the latest version of the Garmin soft strap has resolved that, but in the past others have resorted to using a replacement soft strap from Polar with the Garmin transmitter module.
With the hard strap, rub a little water or spit into the contact pads of the strap before putting it on. This helps ensure a reliable signal when starting out in the cool and before you start sweating.