The ods of getting a pump in/out system balanced is very low IMO
. What you will end up with is one pump doing more work than the other in the long run and either a sump that is slowly being filled faster than it can return or a sump that is slowly being drained faster than it can be filled.
A U tube overflow will NOT lose syphon in a power outage and the only thing to be concerned over is that the sump can hold the back syphon from your sump return tubes. Putting a syphon break just below the water surface of the return tubes (plumbing from sump to tank) will break that syphon when air gets in the holes. You dont need to be worrieda bout that syphon because when power is restored the pump will pump water back into the tank.
You can get a large APC UPS and plug into your main sump pump. That will keep it running during breif power outages. The duration it will keep the pump up will depend on the pumps electrical load and the UPS's reserve capacity.