Science and innovation--the number of old wives' tales that have either been debunked or proven to be harmful is staggering. While the value of instinct should never be ruled out, it is dangerous to rely upon one's instincts too heavily, particularly if they are not reinforced by outside knowledge.
I would say 2/3 science/innovation and 1/3 Tradition/instinct, more and more is being studied and developed about children/growing up it would be foolish not to take advantage of that. But there will always be situations or rules which belong to your culture/family which cannot be solved by science and you will have to trust your instinct.
Use your intuition and logic, too. I can't say it is a combo of tradition/instincts because if I relied on my parents way of parenting me I wouldn't get too far. I use common sense coupled with my intuition. Of course, you need to be on a lookout for what's new, too. You need to know that certain plastics, for example, were recently found to be risky for use with babies (and humans in general) so this is something you need to take into consideration. Although advances in science make our life more convenient, we need to apply our common sense and think if a new gadget won't be proven in 5 years to have some adverse effects on babies' health and safety.