• Shorter in length

• Orange Fabric wristband

• Boukenger Compass Emblem, red & black outlined in white

• Top lid has more bubble shape

• Lid release button is easy press

• Longer in length

• Yellow Plastic wristband

• Operation Overdrive Compass Emblem, red & black not outlined in white

• Top lid has less bubble shape

• Lid release button is click press

• No black light feature

• Thin silver area

• Black light built into back compartment

• Thick silver area

• Thicker back compartment

• More detailed compartment

• More metallic orange paint

• Sounds come from compartment

• Batteries installed in compartment

• Skinnier back compartment

• Less detailed compartment

• Less metallic orange paint

• Compartment has no sound speaker

• Used only for Black Light

• Black On / Off Switch built into overall design

• Red On / Off / Try Me switch has indentation for easy access

• Main piece of changer housing only electronic components
• Thick back component 

• Main piece of morpher housing electronic components and battery storage
• Skinny back component 

• Chrome Gold Dial
• Dial can be turned 360 degrees
• Bit of Metallic Orange Paint on inside
• Silver area wraps all around Dial
• Shorter area for Command Screen & Buttons
• Numerical readout Command Screen
• Two Command Buttons; Combine & Vehicle
• Can call for Gou Gou Vehicles 1 through 13
• Larger Henshin Button with only Dial around it
• Henshin button details are brighter
• Henshin button is simple easy press
• Shorter Siren Builder Formation Sound
• Louder sounds

• Yellow Gold Painted Dial
• Dial can only turn 90 degrees
• No Metallic Orange Paint on inside
• Silver area goes 2/3 around Dial
• Longer area for Command Screen & Buttons
• Three Zord light up Command Screen
• Three Command Buttons; Decoder, Vehicle & Megazord
• Can only call for Rescue Runner Zords
• Smaller Morph Button with black rim and Dial around it
• Morph button detailers are darker
• Morph button is click press
• Longer Flash Point Megazord Formation Sound
• Quieter sounds

Final Judgment

Both Are Even

Overall, both of these devices are great.  The Gou Gou Changer looks great and is exactly what is used on Operation Overdrive, though lacking in the playability somewhat.  The Mercury Morpher, while a bit different from what is used on the show, has a fun Black Light feature and cool new Command Screen.  If you want exactly what is used on the show, then yes the Gou Gou Changer is the one to get.  If you like a bit more playability in the Morpher, go with the Mercury Morpher.  To me, they are both great devices to own.