More info sourced from guys who've done the comparison overseas with pics ...
One source claims the standard RB25DET pump appears shallow, whereas the Neo water pump is deeper, but there is no comment on the blade design/difference. No pics were available to back it up.
Below is an N1 water pump vs OEM RB25DET pump. Blades are obviously different:
The N1 flows less than OEM for a balanced high RPM setup.
The OEM flows more than N1 and is good for street and light track time.
Above is the N1 compared to an EOM Neo pump.
One source says the NEO pump looks like Nissan addressed the flow issue they were having at mid-high RPM (again, no pics/evidence to support this).
Below is a pic of an RB25/RB26 pump (non N1/non Neo)
So ... best way to solve the argument is to get our hands on the 3 types of pumps (OEM RB25, OEM RB25 Neo, N1) and measure volume/capacity/depth, and blade specs and take pics.
So who's got some spare waterpumps lying around?