"Greenland paddle is more efficient"
"Greenland paddle is easier on your body"

Really, let's take a look:

1 "More efficient" ?
There is a Latin term used in the field of logical reasoning "reductio ad absurdum".
All English speakers will intuitively understand its meaning.
"Reduction to absurdity" applied to greenland paddle: since the low profile of greenland paddle is what makes it "more efficient" , the ultimate greenland paddle will be a round stick.
Round stick produces very little resistance hence must be uber-king of greenland paddling.
The fact that round stick will do little to move the boat forward and a lot to produce vortex as it moves through the water
greenland paddle proponents will conveniently skip.

2. "Easier on your body" ?
Yes, since it produces less resistance, our muscles do not work as hard.
What about the frequency and total stroke count? It takes more 'greenland strokes' to move the boat a given distance.
Our bodies do have a hard lifetime limit how many times we can bend our knees or swing our arms. Greenland paddle uses up that limit faster.
Muscles are very adaptable and resistant to wear and tear. The tendons and joins are a different story.
Greenland paddles go easy on the 'sturdy' subsystem (muscles) and hard on the vulnerable ones.
If large-blade paddle feels too hard to pull through the water, there is simple solution: Apply less force.
You will be easier on your body yet still efficiently move the boat, not stir the water.

So why there are armies of die-hard greenland paddle users and proponents?
Well, greenland paddle has it's (albeit narrow) niche: when the wind really blows hard, or there are no materials to make larger blade,
greenland paddle will do.

Still, the large blade "euro" (why it is called this) paddle evolved for a good reason - most of the time and for most people it is superior to greenland stick.

Ah, but it's so pleasant to believe in the "wisdom of thousands-year old traditions", the undiscovered but charmingly green lands of fuzzy logic, the thousands of inhabited planets beyond our solar system, the
bigfoots roaming mountains on the horizon, large monsters swimming in Scottish lakes, Masonic lodges ruling the capital markets,
Elders of the Zion setting fiscal policy and spooky action at a distance entangling elementary particles.

In fact, to the contrary to what Ray Kurzweil writes in the "Singularity is Near", the un-rational and non-logical is what truly
differentiates humans from, well.. the non-kayaking population.