Pennsylvania is far larger in area, has a much greater population, and is home to several large and medium sized cities. Parts of Pennsylvania were once very industrial. The population is much more diverse, and with greater diversity and more people you will inevitably have all that comes along with those things such as more poverty and more crime. There are some very wealthy areas in Pennsylvania as well as some extremely poor areas. Culturally, Pennsylvania is much closer to parts of the upper South and the Midwest than it is to the rest of the Northeast.
Vermont is small, both in terms of area as well as population. It's primarily rural, even the most populous places wouldn't constitute actual cities in most other states. The cost of living is relatively high by US standards, but there's not a great deal of poverty. It's traditionally a very agricultural place, lots of dairy and fruit, but they make a lot from tourism as well.
Those would be the major differences between the two