Chemistay, the decision to go into industry or academia is often several orders of magnitude greater than anything in the $4,000 to $16,000 range, and you don't seem to be finished wrestling with it.
As such, the best investment you could make--far, far more important than anything as comparatively piddly as interest rates or dividends or taxes or treasuries or student loan repayment plans or whether you're risk averse--is to spend some serious time investigating, interviewing, gut wrenching, lit-reviewing, cold calling, interning summer after summer, praying, planning, and generally sleuthing to know whether industry, academia, or a hybrid is the right fit for you.
I cannot overstate that this is the most important decision most sci-tech PhD students make, and many professors do a piss-poor job helping their students through it.