I have a set of Synergy upper and lowers that have been good for almost 4 years. Greased regularly. Never seen this thread and a lot this is from years ago, but those saying that the return to center or steering is stiffer is probably looking at improper installation. This shouldn't be a factor at all.
The Teraflex ones (unless they redesigned) lowers get in the way of larger hub U joints if you upgraded or intend to. Other than that, heard nothing but good things. The Dynatracs are rebuildable, but you can get 2 sets of synergys for the price. How often you gonna rebuild them? I evaluated all of these 4 years ago when I bought mine.
I also heard that balls are a pain in the you know what, so I had a shop professionally install instead of doing it in my driveway... make a difference? Maybe a little...