Might I say how irritating it is when another styles keeps harping how this particular approach (from another style) is not so good (and how ours is better)? I went to a Wing Chun class once, and because the guy knew I had trained in some hard style he kept on saying how Karate or Taekwondo was wrong and that his Wing Chun was better. Gawd. How irritating was that? You can have a lesson without negative reinforcement, you know.
Re: vertical fist. Hey ... we've got that crap in our style too. Notice how I don't eschew Wing Chun tactics, mate. In fact, our last training session featured hand slap drills and these circular punches. It was great to get some fluidity, relaxedness and speed into some 'self defence' drills.
Why is the vertical fist found in our hard style? Well, the essence of the style doesn't necessary advocate punching with a vertical fist. HOWEVER, the vertical fist is part of the punching life cycle. The basic chamber at the side and punch requires that the punch be dragged close to the side of the body, columnate itself to the centre line and then rotate into the target. If you look at that closer, the vertical fist punch starts from where ours 'columnates' and stops before it turns more than 90 degrees into the target.
What I like to remind students is that it is sometimes beneficial to do techniques in a different way in order to learn skills that can be included in our own repertoire. Too much power in the punch slowing you down? Well ... these light relaxed vertical fist type chain punches show that you can go faster by relaxing your upper body. And power generation? If you don't get your hip into it, doesn't matter if you've got a strong arm, you're only hitting with your arm. Relaxedness and dynamic increases in tension are core skills that link both punches. Ours just reaches out a little further and drives the body into the opponent - but it is not to say we can't hit anyone closer.
Learn. Don't bitch!
Peace my brothers.