The difference between Lake Arrowhead to LAX and Lake Arrowhead to BUR is only about 9 miles. Even in traffic, it's such a small difference that you can consider them basically the same point from Lake Arrowhead.

The difference between LAX to Westlake Village and BUR to Westlake Village is only about 10 miles. BUR is slightly more convenient but LAX is certainly not an unreasonably further distance. Also, the least indirect way from BUR to Westlake Village involves some surface streets through North Hollywood, so while the 405 can get notoriously crowded around the interchange with the 101 (where you'd be switching to the 101), IMHO, it's pretty much a wash time-wise.

So, for your airport-to-friends'-house and wedding-to-airport drives, BUR vs. LAX is really a non-issue. The bigger issue is Lake Arrowhead to anything other than ONT.

Be sure you realize that Lake Arrowhead to either BUR or LAX is about a 90-mile drive through the heart of the Los Angeles basin. Without traffic, you're looking at a 90-minute drive (or if you're not a Southern California speeder like me, maybe 100 minutes ), and with traffic, you could be approaching three hours of drive-time.

ONT, on the other hand, is less than an hour from Lake Arrowhead--with or without traffic. (The time is spent mostly on winding mountain roads, and once you hit the freeway, it's smooth sailing; there's not a ton of traffic on the 210 or the 15--at least not enough to significantly slow you down.)

Given that, I'd suggest reconsidering ONT as your departure airport. Check one-way rental rates; some companies offer decent deals for inter-airport drops in the Los Angeles basin.

And if one-way rates are a major factor, I'd actually consider flying both into and out of ONT. It's only about another half hour farther to go from ONT to Westlake Village than LAX to Westlake Village (given traffic, of course), and you'd save a ton of time on your return.