Twilight is definitely my favorite Mane 6 pony
I like her for a lot of the same reasons everyone else does: she's smart, works hard, and can be a great leader. She's always learning something: that trait alone makes her very relatable, as we ALL learn new things all the time!
She's also absolutely adorable when she gets really excited about stuff (I mean, she's adorable all the time, but you know what I mean lol). She hops around and runs around all over the place
Luna is also my favorite Princess, because I find her background very interesting, as well as her personality.
I mean, she used to be a villain! She was feared by all, but eventually, she was freed from the evil and jealousy that controlled her. Now, Luna helps ponies overcome their fears, working hard to show everypony that she is good.
Luna loves to have fun, but also knows when to be serious, and properly displays her authority. To some, she can be quite intimidating, but for those who know her, they know that she is actually kind-hearted and is always willing to lend her wisdom to those who need it.
And yes, she does look cool lol
I just wish Hasbro would use her more, and give her more screen time. She deserves it.