The design on the left has benn called Silver, Mecha, and Robo, in different continuities, and is usually called Silver Sonic, but is the only one to be called Robo Sonic. So, we call him Robo Sonic since that's at least an unambiguous identifier.
The middle one is the first one to be called Silver Sonic, but was originally named Mecha Sonic. Because they are currently called Silver Sonic, we call them Silver Sonic. This is not to be conused with the later Silver Sonic designs that are updates of the design now called Robo Sonic.
The right one is only called Mecha Sonic, and because of that, he gets the name Mecha Sonic.
This is NOT to be confused with the various Metal Sonics…
The design on the left has benn called Silver, Mecha, and Robo, in different continuities, and is usually called Silver Sonic, but is the only one to be called Robo Sonic. So, we call him Robo Sonic since that's at least an unambiguous identifier.
The middle one is the first one to be called Silver Sonic, but was originally named Mecha Sonic. Because they are currently called Silver Sonic, we call them Silver Sonic. This is not to be conused with the later Silver Sonic designs that are updates of the design now called Robo Sonic.
The right one is only called Mecha Sonic, and because of that, he gets the name Mecha Sonic.
This is NOT to be confused with the various Metal Sonics…
Continuity, man.