There are some differences. Some of the Singapore models use a plastic gear in the film advance. That gear can be damaged by forcing the film advance at the end of the roll.
Some late Singapore cameras use a very thin top plate - much too thin, I think.
The Rollei-made Tessars have a better lens coating, I think, than the early Carl Zeiss lenses. I think the Rollei-made Tessars are multi-coated, while the Carl Zeiss lenses are single coated.
Optically, I doubt that you'll see a difference.