Here is my two cents that no one asked for... Please note that I am just an occasional, intermediate rider so take this all with that in mind.
In my experience north NJ trails are grippy and you don't need super aggressive treads, in fact I have had fun on the trails with mtb sized road tires on occasion. If you want to stick to rocks and roots you should be looking for a soft rubber and lots of surface contact i.e. a tight tread pattern (you will also want low pressure to conform to your surfaces). Wide tires are helpful because you have more contact area and can run lower pressures. You want it to be a fast rolling tire so that you are not putting in more effort then you need to. The exceptions to this rule for me are if you are doing steep climbs or fast downhills often. In those cases you will see a benefit with harder lugs with a loose pattern. Big, wide spaced lugs are also good for mud but as has been said here a few times "don't ride mud" because it destroys the trails. My opinion is that really agressive tires have their uses but they are limited and the reason that they are so popular is that they look cool.. Please feel free to hate on this opinion below.