you are very pretty, both look good, which is pretty interesting because most people look better in one or the other.
i can't really decide so I'm going to say what I think of both cause I'm totally procrastinating some homework.
i am a natural light brown like that color, was blond as a kid but on me I prefer blonde-i highlight my hair to a pale blond and I much prefer it that way.
i generally like blond hair better than brown, it's my favorite color.
here's my thoughts on both:
makes your features look more striking, matches your brows better. BUT, brown can be a little dull/boring sometimes (coming from a natural light brunette who went blond and has similar coloring to you but a bit paler) AND I can see it washing you out in certain lights.
Blonde is gorgeous and shimmery, makes your skin look more sun kissed and alive. But, some people have blond bias and think blond looks cheap/slutty/fake/you name it! For all those people, there are many who LOVE blond and it will get you noticed more. Overall, more men seem to find me attractive since I went blond. It brightens up anyone's look.
I think you should also consider the maintenance factor. I don't know your natural color but if you are naturally light brown or even dark blond, light blond hair is a pain in the ass to maintain. even if you highlight to a light blond you will probably need to touch up at least every 6 weeks to keep it looking fresh. and if you bleach it all prepare for monthly maintenance and possible damage.
on the other hand if you are a natural blond, making your hair a lot darker will have awful roots, dark roots don't look great but light roots will look gray and that's worse than dark roots on blond hair. just a thought.
I would have to say the brown(though you would look even better with black hair) because it makes you look more naturally beautifull and gorgeous, to me its sexier and has more of that va va voom effect. The Blond on the other hand looks fake, a little bit like your trying to hard... It takes away from your natural beauty! Don't get me wrong the blond looks good too, but it really doesn't have that natural effect to it.