I was runner up for a WIP grant in 2008. I said I'd use the money for conferences.
I don't think that had a lot to do with my placing.
I think the manuscript/synopsis is most important. Then I think the bit about your life experiences comes after that. If you have some interesting life experiences and if you are able to convey these in such a way that makes you sound interesting/funny/likable then I think that will tip the judges if they have two manuscripts that they can't decide between.
Just my guess.
Someone else asked if getting a grant moves you forward in any way: I think the SCBWI grants are respected so when I say in a query that I've been a recipient, agents can see that I'm not a total newb. I think that's always a plus. I also know that placing gave me confidence that I didn't have before--someone, who is not my mother, likes my writing enough to give me money for it and to say they deem me publishable. That's a huge boost because so often I've wondered if I'm any good or if I'm just blind. I bump into writers all the time that think they are great, but they really aren't very good. So I wonder, "what if I'm like that? What if I'm like those people on American Idol who can't sing but they don't know it? They get up making complete fools of themselves!" Having professionals in the field tell you they think you are good, is a great boost. When I won the grant I had fifty pages written. Placing, even in the runner-up slot, was an encouragement for me to finish the book. It made me believe that at least for a couple of people my premise was interesting and my voice was working.
On the other hand, if you don't win, it doesn't mean you aren't any good. It might just mean those judges didn't like your genre or care for your voice.