There's a parallel of how Metal sonic is always the same as the evil robotic copy to sonic (in the series sonic is changed, metal sonic is always the same no matter what) and he's not really allowed to develop beyond that vs Silver's personality fluctuating in each of his appearance where it can range from serious survivor to nice softie to being just chill version of sonic (since his character/personality is different depending on who's writing him and how writers can't decide what he is like)
There's also how both of them are introduced in games that involves time travel
Dadow is out. Momtal Sonic is in.
(Or you can do both like I am in my Morpheus Shadow AU)












