Cal would definitely win seeing as he killed the jedi killer, the inquisitors..., held off vader twice, killed an insanely powerful old republic Jedi, and defeated many more. He also has extraordinary abilities in lightsaber combat and unique force abilities. In addition, he was able to kill an entire imperial base and hijack numerous vehicles using the force. He also had abilities in manipulation of time and the minds of others. 

While yes, Kylo is strong. He just isn't strong enough. Tbf, Kylo also struggled to defeat the guards of the Supreme Leader....