I'm not sure about the twist rate, but Marlin uses their proprietary "Micro-groove" rifling.... lots of shallower grooves, instead of 5 or 6 deeper grooves. Seems to work well with the rimfires.
The faster twist rifling is good for longer bullets, but in 22 rimfires, the bullet weight/twist rates have been pretty much standardized and perfected. The only reason to have a faster twist rate would be if you planned to shoot the heavier sub-sonic 60gr bullets exclusively.
The faster twist rifling is good for longer bullets, but in 22 rimfires, the bullet weight/twist rates have been pretty much standardized and perfected. The only reason to have a faster twist rate would be if you planned to shoot the heavier sub-sonic 60gr bullets exclusively.