I can't help you on SNA (I live close to LAX) but in the past couple of years, all my UG misses have been between LAX-ATL (5, IIRC). And the couple of times that I used an SWU there were only two people upgraded, so I might have missed those without the SWU.

I usually do LAX-ATL in the morning and ATL-LAX in the late afternoon/early evening and have only missed ATL-LAX once.

A DM on mostly cheap fares (the occasional K in the old days but not so much now)