agentman

Confusion seems to stem from the GameShark brand having appeared on (at least) two entirely different GBA devices. According to this old but seemingly well researched/documented site, the translucent gray/black "GameShark SP" is actually a rebranded Code Breaker device. Whereas (as has been previously noted in this thread), the transparent/clear GameShark and Action Replay GBA devices are the same as each other, but entirely different from "GameShark SP" / Code Breaker devices. Best answer to OP's question would compare a clear GameShark / Action Replay GBA device with a "GameShark SP" / Code Breaker GBA device. Personally I don't know which is more reliable, but I too would be interested in hearing from someone who has experience with both types of devices.