How do SIDs work in New York City?
The LIB4 and EWR4 SIDs, and others like them with just a bunch of VORs, are designed to give ATC maximum flexibility and assume radar vectors. Basically, you take off, make a turn or two to get clear of the airport (and any low obstacles), and then ATC will vector and climb you based on conflicts with other planes at that moment, so you'll probably never get the same instructions twice. There is no real plan; it's literally made up on the spot by each controller for each plane.

The PORTT4 (RNAV) SID is completely different: you have various specific routes to follow and detailed climb plans for each. Many such arrivals and departures in an area will be carefully designed to never conflict with each other (the top and bottom altitudes listed usually indicate there's another SID/STAR crossing 1000ft above/below at that point), so ATC just watches to make sure everyone follows the plan—and gives out shortcuts when possible. Unfortunately, that SID is only valid for two of the six runways, though presumably they're the ones used most often.

Note the latter's lost comms procedure is just to follow the charted plan you're expecting to follow anyway, though without any shortcuts, whereas the former has an entirely different (and uncharted) plan that you'd probably never follow otherwise.