I agree on the topic of higer aspect mainsails being faster and easier to control than the same area in a lower aspect mainsail. Even across the windranges this holds true in my opinion.
Sails going all the way down to the trampoline is not a good idea in my opinion. The benefit is very minor and it makes it harder to get around on the boat (forget end-plate effect and factor in the turbulence + reduced airspeed down there).

I dont know the current status, but are Cobras and Taipans now sailing with a spi downwind in class competitions? They did not earlier and this is another factor to consider when comparing.