damn, I deleted my post so as not to get into a physics discussion, but not quickly enough.
LOL
My hands on experience with was with 60ml syringes. That's what passed for water guns on the farm.
You did the experiment with the same bore of syringe both times, so that is what is expected.
You could generate greater pressure with the smaller needle because the resistance to flow was greater.
This resistance allows you to convert more work into the system as pressure energy (lower flowrate in cc per second), so once it leaves the syringe there is more pressure energy to be converted into kinetic energy. Picture cutting the end off the syringe entirely.... how much pressure could you generate?
the no needle shot was quicker and much easier.
less force for the equivalent displacement = less work. Less energy put into the system.