Hey man. I would say get both sets on Romans. They have extensive footnotes.
The main difference between the two is that Scott subscribes to a viewpoint that “works of the law” applied to Jewish ceremonial laws that set them aside as an ethnic group, whereas the other viewpoint that Sungenis takes is that “works of the law” applies to all law, the mosaic and the moral law.
The “new perspective” has its roots in more recent Protestant theological study, and can be seen in the likes of N.T Wright. It is an interesting viewpoint that takes a more “inclusive” view of “belief” for the purposes of salvation, so it kind of blurs the line between Catholic and Protestant beliefs. Sungenis takes a more hardline traditional approach.
Other differences include the fact that Sungenis takes a hard-line suppercessionist approach. The abrahamic covenant is still valid, but the mosaic is abolished, and is no longer valid. Scott argues more along the lines that the Covenant with the Jews was never abrogated, but that they are merely experiencing covenant curses until they come back to God. This is a vast oversimplification of thhese two viewpoints so I would suggest looking into it further on your own. To my understanding Scott somewhat modified his viewpoints in his tape series on Galations, but I have not listened to it and so cannot personally verify this. I am curious about some of Scott’s ideas, however, and so I just recently bought his disertation on covenant.
You can get Sungenis’ excellent apologetics study bible for download for only 18 dollars if I remember correctly, I am studying Romans now and it is superb. Scott’s stuff can be found at St. Joseph communications website.
Hope this helps a bit.