Ive often wondered the same thing. It is widely accepted that yawls do not point quite as high as sloops, but make up for it on other points of sail. So I uploaded the tracks stored in my Garmin GPS to have a closer look.
Looking at the tracks I quickly realized that I spend very little time tacking upwind. This time of year the wind tends to come from the N or NW. When I have a Northerly, I like to take a lap around Hat Island. When I have a Northwesterly, I enjoy a reach down to Mukilteo and back rather than sail upwind to Hat.
But on closer inspection, I did find some good examples of Ellie tacking. Here were tacking North inside Jetty Island back to the boat ramp. The wind is from the NNW.
And heres a bit of tacking into a Northwesterly.
And finally, tacking into a Northerly, while fighting a little bit of counter current from the outgoing tide.
I dont know what the tacking angles are in these examples. Ill let you be the judge. I know that if I try to pinch Ellie any tighter than the angles you see, her speed drops off dramatically.
I hope this helps answer your question Rob. Comments are always greatly appreciated.