I would say from my experience at the 2 airports, you may be better off at TEB. I'm pretty sure MMU and TEB use the same departure gates, and if LANNA is shut down at TEB, it will also be shut down for MMU. Additionally, I've been told that for every 3 launches off of TEB, MMU may get 1.
The bottom line is, when it seems like the NY airport that you are at sucks at that particular time, they are all sucking at that same time.
You guys are dead-on! All departure/arrival fixes to & from NY metro area have in-trail restrictions depending on traffic, time of day, planet alignment, etc. You may experience a greater delay from MMU since traffic demand is greater at TEB. Yeah, it's supposed to be first come, first served, but you all know how that goes.