I have a Wavetrac, very happy with it. Extremely smooth, practically imperceptible in it's engagement. No drama of fuss, it just gets the job done. Eliminates torque steer too.
I expect others are good, but I can only speak for Wavetrac, they're are also using unique patented technologies, see here:
http://www.wavetrac.net/technical.htmThey're beautifully made, here's mine going in at JKM. My Mk5 is 2009 so was just on the handover to Mk6. It turned out that I have Mk6 transmission which was a surprise.
![](https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi326.photobucket.com%2Falbums%2Fk438%2Fflashp%2FWavetracLSD_zpsa7c07d57.jpg&hash=c7ed3cf4d9853404fe2fdd331fec9c25fb56041d)
There is no doubt though that any LSD is a massive improvement over an open diff. As previously mentioned, buy from one of the bigger names in the business and you won't fail to be impressed.