According to Rolling Stone, Rihanna has sold significantly more singles than Beyonce in 2011. Rihanna also had 8 hit singles compared to just 4 for Beyonce. Looking at the numbers for top individual singles sales, Beyonce's Best Thing I Never Had had 829,000 sales, whereas Rihanna's S&M had significantly more, at 2,580,000.
No, Rihanna is not better than Beyonc�. Beyonc� has been in the industry longer than Rihanna, and has had more time to hone her skills. She has four times as many number-one albums as Rihanna and almost three times as many Grammy awards. Beyonc� has also been in several movies, which proves that she possesses more talents than just singing.
Rihanna may have better record sales than Beyonce, but she does not have the talent of the cultural presence that Beyonce does. Beyonce writes more songs than Rihanna does. She also takes more risks with her music, pushing herself to constantly try new sounds and themes. Rihanna's songs are much more formulaic: if you've heard one, it feels like you've heard them all.
Both Rhianna and Beyonce are talented performers who have their own unique abilities and individual talents. Both have had some questionable circumstances in their lives, from Rhianna's domestic violence at the hands of Chris Brown to Beyonce's occasional anti-feminist lyrics, but the case can also be made that both women are strong, independent entrepreneurs who are generally good examples to follow.