I have similar travel patterns and use both LH and EK as per convenience.

With 6 round trips on SFO - FRA - CCU in paid C, you could get to both United 1K and SEN easily. These really build up on each other, because you can use the 6 SWU's from 1K status to upgrade C to F on LH and use the FCL in FRA, which is great. When traveling within the US, 1K gets you (mostly) free domestic upgrades and SEN gets you free RCC access.

I still try to make 1K, SEN and EK Gold each year. This is easy in my SEN off year (only need to qualify every 2 years), but in my SEN on year, EK may fall to silver, and EK status is the third priority among the 3 above. EK has a better soft product and I do like it a lot, but EK status does not help at all in my considerable US domestic travel.

Also from US West Coast to India, I usually prefer two flights of roughly equal length rather than one super long one and one short one, so LH beats EK there.

LH also arrives and leaves into India (MAA/HYD/BLR are my routes - don't know about CCU) at better times than EK. You get in to India around midnight and can get to sleep by 2am and start the day at 9 or 10am. With EK - you get in at 3am, reach hotel at 4:30am and it's quite a disaster for the next working day. LH also leaves India around 1:45am and so you leave hotel at 11pm after work/dinner and sleep on the plane as soon as you get in. EK leaves around 4am, and the flight to DXB is too short. So you can't sleep properly either before or on the flight.

I have found LH I class award tickets to be easier to get than EK saver J class tickets (though LH taxes/surcharges are high). Finally, being part of *A and earning double miles for paid C in ANY *A carrier is another big plus for LH. And if I am flying Y on most *A, I can get full miles by crediting to United (CO joining means Latin America is also much better covered and with full 100% bonus RDM).

I am also not a fan of the way Skywards changes have been made this year.

Overall, I think EK is a better soft product and I still fly it once/twice a year in J to keep silver/gold, but the bulk of my business has moved to LH and *A more broadly (SQ/TG for SE Asia).

So, I would be inclined to stay with LH if I were you and experiment with 1-2 EK flights a year after status/miles targets are reached on LH/UA. I use my EK miles to upgrade from J to F and treat myself with the suites

Hope this helps!