Wow, that's hard to choice, but I guess Serena since she has a good amount of personality and development especially compared to Bloom.She's also a very complex character.Overall she's a good character quality wise,she's just not my cup of tea that's all.

As for Bloom well.....she doesn't have much going for her.

I really like Usagi. I don't know why a lot of fans seem to dislike her so much. She's very caring, brave (she basically tells two enemies that she's facing at one point to kill her to stop the destruction of the universe) and she acts very human regarding what happens to her. I don't think a lot of fans remember that she's only 14 years old when all the events take place. She cries a lot during the beginning because, well--you've lived a carefree life till now and suddenly you have to kill monsters and find a legendary silver crystal and find a princess and find your other allies without dying and revealing who you are. That's a lot of stress to put on to someone who's already been established as lazy, a cry-baby, and someone who doesn't give that much effort into things she dislikes (school, for example).

She grows a lot more compared to Bloom, who basically relies on the Winx most of the time. Usagi relies on the other guardians at times, but this is mainly to believe in her abilities as Sailor Moon; instead of Bloom's situation where she needs the Winx to save her or assist in battle. Usagi can hold her own and it's because of the strong bond of love and friendship she shares with her friends and boyfriend that she becomes a stronger person and a better warrior, becoming someone who is selfless and willing to risk everything to save the people she loves.

We've hardly seen Bloom in her position as a princess (in regards with her own kingdom), the most we get is her complaining that the royal life isn't for her in the second movie. Usagi is shown to have become a powerful and well respected queen when she's older. She even helps save her own timeline (multiple times) for crying out loud. The most Bloom has done--and it wasn't even Bloom, it was Sky, really--was help break the curse over her parents. I dunno I just really like Usagi.

By far. I don't love Usagi, but I like her well enough. I hate Bloom passionately.

I don't like the Sailor Moon show, so I pick Bloom.

Xena?

Usagi/Princess Serenity is overall a much better character than Bloom.

I don't like Sailor Moon.

I love Bloom but Usa is so cool I love her she makes me so happy and she is so brave and strong and loves her friends very much. She is a role model of mine and I am happy to watch Sailor Moon she is great