Guys, you're all talking about Planars and Sonnars... the Planar is a double Gauss type, and so is virtually every f:1.4 and f:2 50 - 58mm lens.
Sonnars? 105/2.5 Nikkor, the first version. The one which replaced it was a... double Gauss!
A well designed, well made dG will have the same look as any other well designed, well made dG. And so on.
Having handled a ZF lens once, (which was enough) I would buy one only to resell at a profit. The haptics suck badly.