The Metro is the long running Japanese made Sadowsky model. The Japanese Metroline was a short lived attempt to make Sadowsky basses on a factory production line. That didn't seem to go too well and variable manufacturing quality seemed to be an issue. I don't think many were made. Then the Metro's were discontinued and the deal with Warwick was announced. So I think you are probably asking about the Metro basses rather than the Japanese Metrolines.
I've been playing a Metro Jazz RV5 for nearly 8 years and it's a good one. I've been trying to replace it with a lighter bass, but haven't found one that sounds or feels as good. Roger Sadowsky said that the Metros were the same quality as his US made NYC basses. They had the same hardware, pickups, preamps etc, but just didn't have the chambering or customization options. A few years ago I played a chambered NYC bass (sadly with neck dive) but felt my Metro sounded and played better.
I haven't played a Warwick made Metroline.