I only own the 19XR2LW at this time (30 sesh/50 hrs)..& when i had the 21 i did (100 sesh/250 hrs)
Here is the prove.
50h/30s = 1.66 hour/session
250h/100s = 2.5 hour/session
So you have less fun with Core as on average you have shorter sessions..
Tell me why? Doesn't it pull? Doesn't it jump & glide? Doesn't it work on wake style? Your technique & endurance should be better as you have practiced 250h/100sessions your skills & body with the 21 before having Core. I'd expect longer averages on riding as you have new kite what you LOVE
I'd be interested to know how much did you loose money while owning the 21 (purchase price - selling price)? What was the price per session and price per hour?
It is quite bold for you to make claims that Core 19XR2LW is World's second 'strongest / gruntiest' kite surfing kite as you omit Speed3 19m, Speed2 19m SA, even Speed3 15m, Spleene X-19, Big Mama, Dyno 18m what ever are those big LEIs or little smaller but faster LEIs (17m Edge, Infinity, Turbine, Fly etc) and many other. Have you measured them side-by-side? Or you are just making something to become true what you see on local beach with people with many boards, limited kite selection, many weights, many preferences when to kite, many styles of kiting (lawn moving, old school, new school, racing or combo) and many skill levels?
About your fixation to try to prove Core is the best kite for everybody, please give up. You did not like Speed3 21m but still rode it for 250 hours hating it and we already know it. You like Core 19XR2LW and want everybody else to buy it and I'd like to test it but not buying it blind. Good for you that you found something good for you and your wife!
Please post your light wind fun/trick -videos online, I'd always enjoy watching them and have some inspiration for my riding.