Will Leaving a tenure track position after one year for a postdoctoral position at a better location hurt my future academic career?
Not necessarily. BUT, is it worth the risk?
Whether a post doc now will help or hurt depends on many things, such as, even, why you are leaving a TT position now and what your trajectory is. A perfect in every way post doc might help, but I'd think that anything less is leaving you on a treadmill without a sure path to progress. And you don't describe this offer as perfect. And, the &quot;very nice city&quot; aspect doesn't contribute to your career and is temporary in any case.
The goal is to get a permanent faculty position. You have an offer of a TT position which puts you closer to the goal. If it is in a place where you would be happy starting your career then take the TT offer.