Both shields have an SD card slot for data logging. The Data logger shield has a real-time-clock module and a general-purpose prototyping area. It can interface with a GPS module by duplicating some of the circuitry from the GPS logger.
The GPS logger shield is designed specifically for GPS modules. It does not have a real-time clock because the GPS module itself is a very accurate time base.
If the kit is in resalable condition and the GPS shield better fits your needs, then contact firstname.lastname@example.org
to arrange a return/exchange.