We just got done doing 3 days at
Disneyland and 1 day at universal (we are actually at SNA airport waiting for our flight home right now).
There is 4 of us. We flew into SNA and used Uber to get to our hotel on Harbor (at the Disneyland crosswalk) which cost $32.
We chose Saturday for our universal day and used Uber again. It cost $42 for the ride there (park opened at 9 so we left at 7:30) and $52 for the ride back (high demand surcharge)
I looked into renting a car but when I added the cost of the rental, parking at our hotel, parking at Universal and gas, it was actually cheaper to use Uber for our transfers and I didn't have to worry about driving in an area I am not familiar with.