Vented. I'm surprised to see solid rotors on an MB, the last other vehicle I saw with solid rotors anywhere was a 79 Mazda. Vented rotors dissipate heat WAY faster (even faster than drilled/slotted solid rotors), and are actually more rigid because the internal vanes lock two external disks together, making a sort of trusswork that is extremely rigid.
FWIW, rotors don't warp, at least not unless you get them INSANELY hot. Like NASCAR at Bristol rotors-glowing-orange-in-the-corners hot.
Most "warped" rotors are perfectly flat, but have unevenly accumulated deposits from the pads outgassing- it usually starts with someone making an aggressive stop and then sitting at a light for a minute or two with the hot pads clamped hard against the hot rotors.
I've had cars that you'd swear the rotors looked like Ruffles potato chips the way the wheel shook when you touched the brakes. One scotch-brite wheel on a die grinder lightly applied to both sides of the rotor while turning the rotor by hand, and then rinsing with Brakeleen... cured. Years ago, I couldn't believe it when I first read that this was the usual cause of "warped" rotors, but after trying simple cleaning and de-glazing a dozen times over the years, I'm 100% convinced. Now, every time I change pads, I de-glaze and rinse the rotors and I've never had the problem since. I'm also a fan of EBC brake pads which come with an abrasive break-in coating that keeps the rotors from glazing as the new pads bed. And they'd probably break the glaze on old rotors without any manual labor, but I always do my manual de-glazing instead.