Hi Marco,
I personally don't like a lot of belly in my chef knife. Yes, I have a variety of wustoff knives ranging from 1970 is all the way to the present. I even have some of them that are extra wide with a really deep bellies. I use both methods of cutting, both push pull and rocking. It depends upon the task at hand. Obviously when shopping parsley it will be rocking motion but if I am cutting chives to precise measurements I use the push for method. I believe the reason why more chef prefer their rocking motion is that's the first one they learn in culinary school, and it is still taught today. I feel cooks learn the push pull motion when they get out in the field and they learn from some of the old timers who use both the rocking motion and the push pull cut. Because Japanese knives are more prevalent in today's kitchens than ever before, the younger cooks are now learning the push pull method faster. At the end of the day I still like the traditional Japanese style gyuto the best. And in my honest opinion I think you get a more precise cut with this type of knife. BTW I am a pro.