I am considering employment in Phildadelphia. I currently live in NY and work in NJ. What would be the difference in taxes?

I am no tax expert but doesn't one pay (and I assume you are talking about income taxes and not sales taxes or other taxes) income taxes in the state where you reside ? That would be NY right? Some cities, counties impose occupational taxes on those who live in another city, county or state but "commute" into say for example an urban area only to work. That way they can get revenue on those who use their roads, highways, police, or other public services. If my assumtion is correct that you pay income taxes where you live in NY, and neither the City of Philadelphia nor the NJ city or county that you work in currently impose any such "occupational" taxes then the tax effect on you would be NIL. But this is assuming, perhaps incorrectly, that you pay income taxes only to the State you live in. Maybe there is an accountant or tax person who can answer for sure.

Universally, states inpose income taxes on those who work within the confines of their state. So do most cities.

So, you can assume that you will pay PA state income taxes and Phildelphia city income tax (if such a tax exists).

That's the bad news.

The good news is that your home state (in your case NY) will give you a credit, often dollar-for-dollar, for the state and local income taxes you pay to the state/city in which you work. This way, you do not get double-taxed.

You will have to file tax returns for both PA and NY, even if it ends up that you owe no NY state tax.