It's the same as Pixhawk with GPS module. You don't "need" Reach if you already have a RasPi2, Navio+ and GPS antenna. That's the same (and much more) capability as Pixhawk.
My personal preference for Reach is as a static RTK (high accuracy GPS) ground station and antenna tracker system combo, because:
It's a waste of money to pay for an extra Pixhawk/Navio just to do antenna tracking. I say that assuming the price is lower. I guess that depends on bulk pricing of the Intel chips (equivalent to the RasPi part of the Navio). Reading Emlid's blog on the subject shows positive signs in this area: http://www.emlid.com/reach-manufacturing-update/
Reach has a decent processor so we can do a lot more stuff in addition to the obvious RTKLib GPS accuracy boost (already a great feature). I'm thinking about some kind of ground station enhancement like a central/shared telemetry link repeater.
All neat ideas for a university project, good luck and don't forget they also announced educational discounts!