What was the reason for Luna's tears on Star King?

Dubbed as "The Most Talented Girl in the World" by Oprah, singing machine Charice recently made her third appearance on SBS Star King. Her appearance itself grabbed lots of attention, as many tuned in to hear her story of success and most importantly, her singing. However, there was also a strong interest in f(x) Luna's tears, which is now a very big topic. To those of you who do not know, Luna sang Whitney Houston's�One Moment In Time, which was meant to be for David Foster, Charice's legendary producer and now, godfather. Her singing was very good, but was soon after overshadowed by Charice's rendition of the same song. Surprisingly, she was in tears after Charice finished. The cast then tried to cheer her up, by saying "Our Luna is good too." Charice also tried to cheer her up by giving her words of encouragement. Netizens are now figuring out if her tears were from Charice's admirable singing, or something else. The audience at the live set stated, "Luna and Charice's mic quality and volume was different. Her tears were not because of the admirable singing, but because of the comparison." Others have been saying that the studio guest, Jo Hye Ryun told Luna at the recording that she had to be here in Korea which in other words meant that she could not succeed overseas, and caused her to burst into tears. I personally think that Luna was sad about the comparison and felt sorrow. But like Charice told her, the only person to win is yourself. Luna is young and it hasn't been long since she had debuted. She is definitely a good singer, and there is much more room for improvement.