You need pay whatever is higher. If you register you car in Pen, then you need make sure the tax is 7% or you are responsible for the difference.
Both are not good deal. You can get a killer deal with Accord if you press harder. It is 1 year old model and 08 has the new model so you offer than $19000 OTD and see what is going on.
Camry you can settle at $19500 OTD since it is same model from 07.
LISTED ARE SALES TAX from Maryland and Pen.
Maryland
Maryland has a 5% state sales and use tax with exceptions for medicine, residential energy, and most non-prepared foods. Currently, many services (ex. auto repair labor, haircuts, accounting) are not taxed although the legislature is considering extending the tax to those services as well.
Pennsylvania
Pennsylvania has a 6% sales tax rate. Allegheny County and Philadelphia County have total sales tax rates of 7%. Food (not-ready-to-eat), most clothing and footwear, medication, funeral expenses and preion drugs are among the items exempt.[39]