I've flown into LGW on DL and LHR on KL, AF & AA. I get totally confused as to which terminal is which at LHR but they have all been equally chaotic to me. LGW is a piece of cake, especially the north terminal that DL uses.
LGW will grow on you. It will be different, but that can be good. Given a choice, I'd pick LGW over LHR any day. The best part is that once you get thru immigration and baggage claim/customs, you can sit down on the train for a relaxing 30 min ride to Victoria without worrying if you will miss your stop.
If you fly the route with any regularity, you should know that the check-in and gate agents are mostly contract employees from ServiceAir. For those times when you need a real DL employee, look to the left of the check-in desk for the separate DL counter. The staff there are generally very helpful.