I'm looking at flying from LON to AMS on an early morning KLM flight. According to the timetable, I have the following options:

KL1000: LHR 06:30 - AMS 09:05

UK2222: LCY 07:40 - AMS 10:00

Although the LHR-AMS flight is scheduled to arrive 55 minutes earlier than the LCY-AMS flight, I suspect that both flights usually arrive at roughly the same time, given the huge difference in congestion between LHR and LCY. Is my assumption correct?