For CLA, traction would not be a major issue in snow/winter, just like not many people concern too much about Passat, Camery, or Accord's traction in winter. 4Matic would be beneficial, but not as dramatic as in RWD cars..
from MBUSA web:
Front-wheel drive
from MBUSA web:
Front-wheel drive
Standard
A first for Mercedes-Benz in the U.S., the CLA's front-wheel drive system is an ideal match for the car's sporty demeanor and efficient packaging. Impeccable calibration of the Electronic Stability Program (ESP®) and Electronic Traction System (ETS®) enhances tire bite under hard acceleration, while equal-length driveshafts virtually eliminate undesirable torque steer. The compact powertrain design also allows for generous cabin and trunk space within the CLA's sleek profile.
