Regarding the Oceanic NEO Second Stages...they both have the same list of "features":
- Pneumatically balanced second stage with virtually no breathing effort
- Advanced composite construction for rugged durability and light weight - our lightest second stage at only 5.7 ounces (without hose)
- Ergonomic Adjustable Venturi Switch (A.V.S.) for simple Dive/Pre-Dive Adjustment
- Patented Orthodontic Mouthpiece with high-density bite tabs for increased comfort and reduced jaw fatigue
The FDX-10 and CDX-5 First Stage say the same thing:
- Effortless pneumatically balanced breathing paired with a compact overbalanced diaphragm first stage
- Nitrox compatible to 40%
- Oceanic’s DVT (Dry Valve Technology) eliminates corrosion of critical internal components
- Designed for extreme depths and cold water
The FDX-10 seems like the newer model and physically looks different...so they changed up the design some...but kept the same features.