Which program do you want to go to, and which city would you like to live in for residency? That's how you should be picking which hospital you do your peds sub-i in. If you do well during your sub-i there, they are more likely to accept you for residency.
Enjoyed my sub-I experience at Stanford, so I recommend it, especially if you enjoy the challenge of managing complex patients. An acquaintance did an elective at Children's Oakland (not sure if it was an AI or just an elective) and had good things to say about it. UCSF also offers a sub-I but I don't know much about it.