Hey - I know exactly what you're sayin. I've had the same challenge. Ultimately, I think the PS should focus primarily on the WHY. Don't waste more space than necessary describing the WHAT, WHEN, WHERE, WHO, HOW, etc.
Of course you'll mention those formative experiences in your PS, but remember that you have 700 (and, lucky for us, 1500 more) characters to describe and discuss them elsewhere (namely, in the 15 things).
After having several people read my PS, almost all of them agreed that I was allocating too much space to my story, and not enough space to my synthesis of that story. "Wow, you've done a lot of interesting things...BUT WHY THE EFF DO YOU WANT TO BE A DOCTOR?"
I think the reason I keep leaving some of this stuff in my PS is because I'm paranoid that somebody might not read all of my 15 things, especially with the new longer versions. I don't want to miss an opportunity to make myself stand out, and I feel that there is less variance in people's WHY's.
Still, I'm starting to agree with everyone who's given me feedback - I gotta answer the question, not just write something fascinating about myself.
Question for the Wise Elders: Is it safe to assume that most people who read our PSes will also read our 15 Things, or are these tasks typically divided up? While I'm at it, do we have any data on how thoroughly each of these things are read?
I'm guessing like a minute of their time per week we put into writing it.