I drive a 2010 Jetta TDI and my wife has a a 2012. The is a noticeable difference in the handling. I'm looking to sell back my 2010 Jetta and get a Golf but I don't want the crappy rear suspension her 2012 has. What year did the Golf and GSW go to the new style rear suspension that the Jetta received in 2011?
The short answer is they didn't. But don't attribute your impressions of handling feel to the rear suspension on the 2011-13 Jetta Sedan. That car was made to a different set of specifications than the 2010 sedan. They wanted to attract buyers who were cross shopping Toyotas and Hondas. So the car is softer, less responsive. Does the rear suspension make a difference? Sure, but not that big a difference.
In 2015 the Golf and Golf Sportwagen got a trailing arm rear suspension similar to the MKIV and earlier cars, because of the need to find space for the Urea tank in the TDIs. All the other Golfs and GSWs in the US have IRS. The 2011-2013 Jetta Sedan had a Torsion beam rear suspension, quite different from the trailing arm suspension in the 2015s. And in 2014 the Jetta Sedan got IRS (GLI always had it). The 2015 sedan also has IRS.
I've owned a 2006 Jetta, 2012 Golf (IRS), and now a 2015 GSW (trailing arm rear suspension). And my daughter had a 2013 Jetta 2.slow for a while with the Torsion beam rear, which I used to drive a fair amount. I've also had a bunch of earlier TDIs (still have 3) with trailing arm rear suspension. I've driven them hundreds of thousands of miles, and many miles on race tracks. With the right dampers the trailing arm rear suspension works very well. And it has the added benefits of being simple and durable.
Drive a new Golf or GSW and see what you think. I suspect you'll be pleasantly surprised.