I faced a similar decision a few weeks ago when I was deciding between Harvard and Scripps (also for a PhD in chemistry). This may not sound incredibly insightful or helpful, but when it comes to two great programs such as these, you have to go with your gut. What that means is that it's best to ignore all of the "fringe" stuff, such as weather, institutional fellowships, differences in pedigree etc.
Pete Schultz gave me some great advice about making these types of decisions. He told me that the only two things that matter are "the science and the people: what research will you be doing and who will you be working with and for?" That may be too simplistic of a philosophy for most cases, but the general idea is that the best fit for you is exactly that...a place for you and your personal preferences. Don't let things like rankings or ill-informed family members influence your decision because you will be the one living and working wherever you choose for the next 6 years.
Therefore, I think the best person to ask about making this decision is yourself. If you really feel that you're 50:50, you can always try the trick where you literally flip a coin and gauge your emotions (whether they be excited, apprehensive, or whatever) upon learning the "coin's choice." Personally, I didn't have to resort to that because I grew more and more excited about Harvard every day to the point where I could confidently make a final decision.
Regardless of where you choose, know that you'll end up at a phenomenal school with one of the best programs in the world for the research in which you're interested. It's a decision without a "wrong" choice, so don't stress and go with your gut.