I will be driving to SNA airport on a Monday morning for a 1:00 PM departure.
Which commute would be easier:
Driving to SNA from West Hollywood OR
Driving to SNA from San Diego area ?
Estimates of driving times would be welcome , too !
I am visiting LA area and San Diego on
the same trip and need to decide which
area to visit during the final days of my trip.

I'm guessing you'll need to allow time to fuel and drop a rental car, plus a 90-120 min. advance checkin time, thus you'll need to be somewhere around SNA by 10:30.

That said, you probably won't have a great deal of trouble leaving either W. Hollywood or San Diego (downtown?) to get there on time. I'd probably leave W. Hollywood around 9, just in case you hit really bad late rush-hour traffic. If you don't, you'll probably get there just after 10 using 101/5/55 (I'd never suggest 405 past LAX in the morning).

Coming from the south, I'd also allow 90 min. unless you're starting on the north end of the San Diego area (La Jolla etc.) Again, you might breeze in an hour later, but then again you might not.

If you want to be extra secure, then probably I'd pick San Diego, mainly because in my (recent) experience commuting between W. Hollywood and the SNA/Newport area, I've found getting to and on the freeway system in the W. Hollywood area is a significant pain in the brain. Leaving earlier from W. Hollywood doesn't get you anything because of commuter traffic.

The drive from San Diego to SNA is way, way more attractive, anyway.

Gardyloo's observations are all good ones. The 405 will clear out some after 9 AM (making for a much more direct drive-- 405 south to SNA), but the 101-5-55 drive is pretty easy and quick as well. I would say that whichever route you choose, leave no later than 9:30 AM. SNA, being a somewhat mid-sized airport, shouldn't have the security snarls you see at a place like LAX-- depending on the airline you're flying, of course.

Having said all that, the drive up from SD is indeed very nice (with Pacific Ocean views up through north SD county and southernmost OC), and also relatively easy (5 north, then take the 405 north to SNA). Factoring in possible tie-ups at the INS/Agriculture checkpoint, I'd also plan on leaving SD at 9:30 to get to SNA on time.

I should note that I'm assuming you get to SNA at 11 AM and get the rental return accomplished and get through security. That is, give 90 minutes on the road (and know that, most of the time, you'll beat that estimate).

One thing I should add is that if you're not familiar with the immediate SNA area, and/or are returning a car off-airport, be advised that the street patterns and directional signage around the SNA entrances, quite frankly my dear, stink. Depending on the direction you come from, and especially if you make an initial mistake, it can be quite easy to be on the wrong side of a very wide boulevard, with OC drivers, all trying to be the first ones to the accident, between you and the lane you need to be in. Thus miles-long counter-intuitive looping results. Sometimes you can breeze right into the airport circulation road, other times it seems like it was designed by marketing types from LAX.

If you are in West Hollywood headed towards SNA you have a plethora of freeway options should a big rig go belly-up on your first choice route.
Coming from San Diego you've really only have one choice, I-5.