The National track has several sand sections, several clay sections and others mixed with both. Because it is a national style track it is fast with many sweeping turns. The Vet track is mostly clay which is probably closer to what you have been riding at Sleepy Holliw and other Pa tracks. Both tracks are fun to ride but yet very different. On the practice days both tracks are open to bikes and quads but on race day we are using the National track for bike racing and the Vet track for quad racing. Hope this helps.
http://www.njmpfod.com