Is Oracle Team USA's boat faster? Or are they just sailing better? Or are Team New Zealand just not sailing well?
The answer is all of the above. However, there are other considerations which show Emirates Team New Zealand are still capable of grabbing that frustrating point.
Oracle have re-engineered their boat and are significantly faster than they were earlier in the regatta.
The best analysis suggests changes they may have made include:
Altering their wingsail so it has more of a twist in it, as Team NZ's does. This gives the boat more power.
Re-jigging their daggerboard systems and got it working perfectly.
Improving buoyancy of their bows, allowing them to skip over the water better and not be so bow-down.
Being more astute about setting their boat for the conditions.
This is one of the trickiest parts of the 34th America's Cup.
The teams do their weather forecasting and set up their boats accordingly and Oracle have been doing both things better lately.
Increasing acceleration to the first mark, giving them a head start in making it first to the vital bottom mark.
This has been apparent throughout the match but was best seen yesterday in race 15 when Dean Barker led Jimmy Spithill over the line but Oracle sprinted away to round the first mark three seconds ahead.
In boat handling terms, their biggest weakness was their tacking. That has now been corrected and they are highly competitive in that department.
Spithill is now also clearly out-thinking Barker in the starts.
The Kiwis have two port entries to the start box today and it will be vital for Barker to make a mark there. Literally.
In a day with tricky and flukey winds, the Oracle crew also did better picking the wind shifts and staying out of wind "holes" that see boats stop like a bicycle with a flat tyre.
But that's sailing - one day you are a wind wizard, the next a blowhard. Team New Zealand tactician Ray Davies found some big winds yesterday but also fell into some holes as Aotearoa two or three times seemed set to reel in Oracle.
So the lesson is that no one should be banging their head on the table and bemoaning that Oracle are set to make the comeback of the century.
They may well do - but here's what Team NZ have to do to win that last, final, elusive and heart-breaking point today:
Mode their boat for the conditions - expected to be 10-14 knots.
Win the start.
Be first to the bottom mark at the end of the downwind leg.
Pick the wind shifts better.