Emerald is the first game that has the Flame Body ability halve the amount of steps needed to hatch a egg. So hatching is faster. Otherwise all 5 of those games have the same shiny encounter rates. Edit Emerald is also the easiest to RNG abuse of the the gen 3 games.
Mind uploading the both Scyther? It’s easier to find the issue if we have the actual pkm files. Also did you try and make it from scratch in Omega Ruby or did you drag and drop it into Omega Ruby?