Slippery in terms of the mat's resistance to moving around on the floor, or in terms of the amount of friction between the mat and your feet?
If you meant the former, for me, the 3D Maxpiders have stayed put, but the car they're installed in has floor mat retention posts sticking up out of its base carpet that the 3D Maxpiders mate up to with plastic ring-lined holes. The 3D Maxpiders also have a velcro-like "clingy" underside that's intended to grab onto the underlying carpet to help them stay put. I actually find the surface a little annoying when I'm taking the mats out and putting them back in when cleaning them, since it's somewhat abrasive. In comparison, the Tesmanian mats do have small strips of velcro-like material at the four corners on their undersides, but that's it. They're pretty smooth otherwise. Honestly though, the Tesmanian mats are contoured to fit the shape of the floorpan so well, and are so snug when in position, that I seriously doubt they'd be going anywhere, even without the velcro-like stuff.
If you were talking about the amount of friction between the mat and your feet, I haven't driven with the Tesmanian mats in the rain yet, but I can guess that the rubber of the Tesmanian mats will probably be more slippery underfoot when wet compared to the 3D Maxpider mats. It's just the nature of rubber. The 3D Maxpider mats have a more textured almost weave-like surface, so they would probably provide more friction when wet, but that weave-like surface is the exact thing I dislike the most about them; it makes them a pain to keep clean, since all the little pits in the texture tend to collect dirt and dust. Simply wiping them down with a wet paper towel isn't enough to get them clean; they have to be scrubbed down with a brush and hosed off to really get down into the pits to get them clean, and even then it's still not perfect. The Tesmanian mats shouldn't have that problem, since the rubber surface is far smoother in comparison. That's the main reason I picked them over the 3D Maxpiders this time around. I also like that there's no logo on the Tesmanian mats, nor are there any holes through which the studs securing said logo penetrate (kind of defeats the purpose of having an all weather floor mat in the first place if there are holes in it under the logo).
Sorry if this is off topic for this thread...