You are referring to the unit around your waist that holds a dildo or vibrator, correct?

Strapon harnesses are better because: more secure, can use different dildos, look sexy and feel powerful seeing dildo hanging down. Just need get one that will hold the dils in your stash and future stash. I like the Lux rider. It can hold various sizes. Details on my review.

Strapless are hard to keep in for a good length of time. They're good for brief encounters. They're good in spooning position.

With harnesses one can have very long sessions. I have several and use more than one per " date"