I have the highsports silverlines on my Gttdi went from standard to coilovers so couldn't give you advice has to the difference.
The collies should last you longer than springs and standard dampers and you can service the coillies has for performance thats upto you if your looking for a track weapon then get the coillies corner weight setup, taking each corner by its weight and setting the coilover by this, you may not get the heights bang on this way but it will handle better OR the highsports are one of the best for getting down low on the mkv golf if you want LOW then get the highsports.
Darren