We chose to use the standard adhesive tape-backed curved mount base because it fits the most helmets out there, but because there are no standards around helmet shapes, nothing is truly universal. We find the adhesive mounts hold much firmer, are less bulky, and less expensive than strap mounts. Strap mounts don't work on a surprising number of helmets because of the number and orientation of vent holes, plus some MIPS style systems can block vents entirely. We went with the solution we feel optimizes on-trail performance and minimizes the cost of the light system to purchase. If you have multiple helmets, multiple adhesive mounts can be purchased for less than the cost of a single strap mount.
Good news is, since we used a standard "action camera" mount interface for our helmet lights, any accessory GoPro compatible mount should work, and you can pick up a Vented Helmet Strap Mount direct from GoPro for $15 if you so desire.