The Merritt Pkwy is usually pretty good for me...but I almost never drive it during rush hour.
Also, when there is bad weather, always avoid the Merritt. Always some jerk going too fast that wipes out and blocks up traffic for miles. Same on Saw Mill heading to the Tappan Zee.
I like using route 136 in lieu of the Merritt and route 35/100 in lieu of the Saw Mill.