I don't particularly mind Frozen (save for the ridiculously vocal fanbase who just can't, well, let it go, seriously it's been 2 years already), but I'd say TLK is vastly superior in plot and heart. Frozen somehow felt incomplete, and the whole sister dynamic felt very unbelievable to me (I believe
this comic illustrates this better). I'd say TLK had more believable interactions and the plotline was grander and more interesting, especially the universe it established; personally I'm far more curious about TLK's lore, while I just can't bring myself to wonder about and care about Arendelle.