It's hard to believe that these two fantastic neighboring towns are located in different counties. Summit is located inside of Union County while Short Hills finds itself inside of Essex County in NJ. One would think that with the difference in counties you would find a huge difference in the taxes you would pay. However not so much so, in this regard.
The current tax rate in each of the towns:
Short Hills (Millburn Township) - tax valuation = 87.41%, tax rate = 2.105%
Summit - tax valuation = 44.74%, tax rate = 4.217%
To put it frankly, if you purchased a home for $2M there really wouldn't be that much of a difference. In Summit, your taxes would be approximately $38K and in Short Hills $37K. So when deciding between these two towns as your final destination for your New Jersey dream home, taxes can not really be the deciding factor here.