Sync-on-luma (RGsB) : very good and the cheapest : £17.99 + shipping
RGsB : R,G and B have their own wire, the sync signal is combined on a separate wire (sH+sV)
Correction: RGsB is sync-on-green, where composite sync is muxed to Green; and RGBS has composite sync on a separate wire.
Additionally, the composite sync signal provided by consoles for RGBS is typically composite video, which carries composite sync by design. Luma also carries composite sync by design, and is sometimes preferred over composite video by retro gamers because it causes significantly less interference to the R, G, and B signals compared to composite video.
Clean composite sync should be the most preferred, but it’s really only required when using your consoles with professional video gear, like Extron’s RGB interfaces, and it’s extremely rare to get clean CSync from a console without a hardware modification; often aftermarket/boutique cables that offer clean CSync output use a sync stripper to remove video data from composite video or luma, and those sync strippers can sometimes cause compatibility issues with other devices, like the gscartsw when its sync-regeneration is enabled.