I’ve run Marta SL’s on my Spark for 2 years now. Initially with 180mm vented rotor up front and 160mm std rotor out back. Now 180/160mm std rotors as I gave the GF the venti as I didn’t really need it on my race bike.
I also run Marta SL’s on my Ransom with 203mm venti front, 180mm std rotor out back.
The brakes are super in both applications, one for xc race, one for trail/AM riding. Both applictaions give well modulated and confident stopping and IMO better than the 06 Louise FR’s that I had on the Ransom previously.
Only problem i’ve had is on a super muddy enduro race (4 hrs of mud plugging) was dirt in the lever bodies and calipers meaning I had to give them a thorough squirting with my water bottle to get the wheels turning freely again as things were binding.