They basically mean all the same but can have a different nuance.
Especially because - that’s your opinion and you’re trying to state why did u say such thing
Ex. -I wonder how police officers find the Chinese missing girls.
-Because they all look the same (that’s pretty racist btw)
When sounds more general, like you’re just stating a fact.
In my opinion, since in the first example might have a feeling that before things weren’t okay, but now are.
But tbh the difference is really small and you don’t have to worry which one to use, you just “feel it” You could even use “If” in those examples