Is body wearable antenna same as directional antenna?
If the antenna is truly isotropic then the body may become the radiator under where it is attached and the surface the radiator above where it is exposed.  Where it is attached and how may affect the results thru the body and thus be different from the results alone inside a chamber.  

Whereas Vertical dipole antenna on your hat radiates like a donut omnidirectional in the horizontal plane it might look like a lightning rod or just a rubber ducky on on your wingnut hat.  In Theory a dipole has no gain looking down both ends of the pole and increases to 2dB. THis antenna has a loss from -6 to 0 dB in both elevation and azimuth which standalone is fairly isotropic and less noticeable but less gain than a vertical dipole. or monopole. (1/2 or 1/4wave)

So  if you’re only looking to improve cell signals for one carrier, go with a directional antenna with high gain over a narrow elevation but omnidirectional for azimuth. It's more powerful and doesn't take much work to find the general direction of the cell tower.

If you’re looking to boost all the major carriers, go with the omni. And especially if you already have pretty good signal but building material is the main problem obstructing your 3G &amp; 4G signal, then this is a winner, too.