I would recommend that you give DL a try for your domestic travel. Keep your TATL on LH (or LX) and apply these miles to M+.
The DL overall travel experience from beginning to end is really good. I just cannot say the same about UA; with UA, something always goes wrong. To me, DL treats me like how pmUA used to treat its elites.
And, yes, you can make DL work for you out of SFO. I will add that the SFO DL SkyClub is probably one of the best domestic airline lounges. No domestic UA Club comes even close to the SFO SkyClub. I also like that in many airports I have a choice of United Clubs and Delta SkyClubs.
My upgrade percentage on DL (when doing CPU) far exceeds that of UA (when using RPU and GPU instruments on higher econ fares). On UA I have XX RPUs and XX GPUs remaining, and these certs are proving to be worthless.
Yes, others will chime in on how bad the SkyMiles program is. It can be bad. However, I make it work for me. For award tickets many times UA shows no availability, but DL shows availability – and vice versa. So far for 2017 I have redeemed more DL miles than UA miles – mainly because DL had availability and usually at a lower redemption amount than UA.
Yes, if I applied my DL spend to my total UA spend, I would be in GS territory. But, I won’t do that. I really do not want to spend more time on UA (in its current state) than I have to. DL is just a much better overall experience.
Best of luck to you.