According to Sea Kayaker "Fit paddler can paddle against 3 lbs of resistance for long distances"
"Only a few can work against 5 lbs for long distances"
The fast vs. slow boat comes into play at the top end of the speed spectrum. Kayaker in a kayak that produces 8 lbs will win against kayaker in a boat at 9.
At the slow touring speed 2.3 vs 2.1 makes no practical difference.