It depends on my mood and whether I need to make any stops on the way into work:
Most mornings, local roads to PA-413 to I-95 to US-1 in Lawrenceville, NJ. Then a few miles on 1 and some local and county roads. The return trip in the evening is the same route in reverse. 7 lights in PA and 6 in NJ. Around 30 miles and 40 minutes (give or take 5 minutes depending on traffic, the lights, and prevailing speeds on the Interstate.
Some days it's US-13 to US-1, then the same local and county roads from there. Around 24 miles and about the same amount of time. 5 lights in PA and 7 in NJ.
I prefer I-95 because traffic tends to run at a more consistent speed (plus it's a much safer highway, anyway, with longer sight lines and wider curves -- even if some of my fellow Pennsylvanians don't seem to think so and slow down every time there's a curve). I am looking forward to the improvements that are forthcoming during the Scudders Falls Bridge work, though. It'd be nice if PennDOT would raise the limit through that area to 65 as well, since I think it's a much safer road at that speed than the Turnpike (and it's way better than the 1 and 13 freeways, which are both 55). At least the PA Troopers seem to enforce it as if it were a 65 zone.