I don't know, I've always found the 405 to be much worse than the I-5. I imagine the I-5 can be bad during rush hour, but not 24/7. There's a lot to be said for taking the direct route.
let's be real here: they're both terrible. both.
the 5 is bad 24/7. my shifts have had me driving down there at 5am on some days. and you're right, no traffic then, but for shifts starting after 7am, i never ever ever take the 5; i always without fail get stuck in 1-2 hrs of traffic. yes, hours. not including regular drive time.
going home, when i work evening shifts, you can't even take the 5N, it automatically diverts you to the 91W right now, and has for several weeks. there must be road work somewhere.
but coming home, yes, it's the same. i used to take the 5 coming home, and without fail, whether it was 10am, 2pm, 9pm, even 1am, i have always hit significant traffic. and it's almost always worse coming home then going down.
when i left this morning, i took the 5 until the 91, and yes, at 1030am, i hit traffic on the 5 until i got to the 91.
then i drove the bulk of my ride on the 91.
and hit traffic again once i got off to take the 405 to my exit. but never on the 91. almost never, anyway.
5 days a week, which means 10 trips weekly. i know my traffic patterns from LA to Disney, in both directions. well.