I used to do that run frequently. EWR is quicker, but not by alot, 20 or 30 minutes maybe. At rush hour, as others have said, Route 1 is congested in whatever direction you go.

There used to be a company called the Princeton Airporter that ran a shuttle service to EWR and JFK and one of the pickups is the Hyatt right there in Carnegie Center. I just checked, the name's changed and it's now known as (both) State Shuttle or Olympic Airporter. Price is about $36 one way, with a discount if booked on-line. Also, the building next door used to have shuttles running to the train station but I'm not sure if it's solely for GE employees or even if it's still provided.

For the short trip on the train, I imagine Amtrak over NJT wouldn't be a huge issue.