I agree that the bass is more controlled with Sonarworks. The bass is a little flabby (woolly?) with Arc.
The Sonarworks setup is easier than Arc. An on-screen graphic shows you where to move the mic, then it starts the measurement automatically when it has sensed that the mic is in the requested position.
Sonarworks: Having one plugin in your master with the ability to switch between headphone curve or speaker curve
is great.
Arc: A little more flexible with setting up a user-defined EQ. I like to boost the highs a little for my aged ears.
Sonarworks needs a little improvement in the user-defined EQ options.
Sonarworks: The new zero-latency mode is an excellent feature.
Sonarworks says that it may use more cpu in that mode but I have not noticed this (yet).