Last year I got one tenure-track job offer and accepted it, even though I wasn't thrilled about the position. The institution allowed me to defer my start date by a year, so that I can complete a postdoc. I fully intended to start the job when I signed the offer.
Now, several months later, I received a tenure-track offer from a top institution with resources and benefits that can never be matched by the institution that is currently waiting on me.
I understand it is unethical for me to bail on Institution 1. At the same time, I only have one life and one career and don't want to sacrifice my prospect for loyalty to an institution where I haven't even started working.
What would you do?
EDIT: What are the range of professional consequences I can expect if I switch to the new institution?