By the chemistry, the acting and the meant to be...
Honestly, I love both: great actors, chemistry and they look so cute together...!
I think that in their movies/dramas KathNiel look more adult, serious (even if they’re younger) and like a old couple that still, after years, love each other. And that JaDine is more like a serious/new younger version (even if they’re older).
acting and chemistry wise I would really go with KathNiel
both love teams are great, each performance they have in their shows have impact but for me there is more "kilig" factor with KathNiel than JaDine, i love how the real-mature-new kinds of love are portrayed as it speaks to the current generation and real problems but I would still choose KathNiel as an escape to the reality as the showcase more of imaginative playful love you would want to have someday