I generally don't like Katy's music much and I'm not too much into 'empowerment' songs(there's been too many now).
Applause is an objectively good,catchy and addictive pop song( I don't know how a pop fan can legitimately dislike it).But for some reason,it didn't really satisfy me.It doesn't seem to have that LEAD single factor or bigness.
Anyway,to answer the question,Applause by a good margin.
I expected more from both but I think that while Applause being catchy It's weird at the same time and It's a bigger grower than Roar therefore Roar is getting boring faster..
Applause by far for me. Roar is more radio friendly and awfully safe (I like it better than most of her singles tho). Applause is really great and I hope it will slay although I am not sure if GP can really appreciate it.