Like many software programs, what’s “better” will mostly depend on your strengths and your needs as an artist. For example, Finale is often the top choice for Classical Music Composers while Sibelius is often preferred by Screen Composers and Film Scorers.
That said, Finale has a reputation for having an insane amount of features, and thus being more “powerful,” whereas Sibelius is known for its speed and ease of use. Overall, Sibelius does seem to be the more popular among users, and there’s a reason for that.