My SCAR15S has a lot less felt recoil than my m4.
Love both m4 and SCAR but the win goes to the SCAR.
I shot the ACR but did not like the feel and ergonomics. Also did not really like how the ACRs barrel is held unto the receiver.
EDIT:
Also since you did not mention which SCAR, there is the SCAR16S(5.56mm) and the SCAR 17(.308Win)
Just shot both today. Over 4000 rounds through the 16S and near 900 through the 17s. Been flawless and a true pleasure to own the SCARs.