Depends. It's okay not to know what you want to specialize in after 4 years of undergrad, especially if you don't have a lot of research experience yet. Honestly, most people don't.
If you do write about a very specific topic, it'll look good iff:
1) you demonstrate a solid understanding of the field;
2) you propose a novel or at least interesting project; and
3) the school you're applying to has researchers with funding in that area.
That's my take, anyway.