Assuming you can charge a work day for the travel day, I am a fan of the daytime. I did this a couple of times when I lived in DC when United had a daytime IAD-LHR.My jet-lag avoidance routine was to go to bed the prior night at a normal time, then try and wake up a a bit early and usually do some work before heading to the airport and drinking some lounge coffee. Take the flight and usually stay up until normal bedtime in Europe. Other than loss of a day it was great.