What would be a better time to drive to Las Vegas from El Segundo, CA on a Thursday at 3:30pm or 6:00pm?

3:30!! Moved from southern Ca. to here in Vegas & have driven many times! More people get off around 5 pm than 3:30.

if you leave at 3:30 you will be driving through the worst of everyone coming home from work but if you leave at 6 you will get there later but it is better to leave at 6 to miss the traffic because you will end up getting there at around the same time because the traffic between 4-6 is horrible

Previous answer makes a lot of sense. I usually wake up really early and drive in the morning. There is no traffic and I get their quick.

The earlier time would get you in at a decent hour, but either way make sure the hotel hold your room for a late arrival.

Coming in from a 3:30 time would miss the traffic at your end and hopefully the rush hour freeway traffic here.

3:30pm

I always leave in the early a.m. to avoid traffic

I agree with the people stating that 6 pm is a better time. Whenever family comes to visit me (from Riverside, CA) they either leave really early in the morning or later in the afternoon so as to avoid the after work traffic. Granted it isn't like LA traffic but considering that there are only 2 freeways in the city, they get really jammed.
Just be glad that you decided to come on a Thursday instead of a Friday. Those days I just avoid driving altogether! ;-)