You can find all default styles here: CSS2.1 User Agent Style Sheet Defaults.
If you investigate the list closely, then you'll notice that the browser-specific margins are only set for HTML-standard block elements and that nowhere a browser-specific padding is been set. In other words, the padding: 0 is superfluous. But indeed, the margin is the most disbalanced among browsers, to answer your actual question.
I am probably going to tread on someone's toes here, but in my humblest opinion using a CSS reset stylesheet is ridiculous. You would have to redefine most of those margins (and paddings) yourself anyway. You could as good just learn and keep yourself the rule to define yourself the margin (and if necessary padding) for every block element which you're going to use in the document.
As to the remnant of the reset:
The border: 0 is superflous as well. The <hr> and the most form input elements are the only elements which have a default border. Without it, the <hr> is invisible (actually, this fails in IE6/7) and the text input elements on a form with same background color are invisible as well.
The outline should certainly not be resetted, it breaks accessibility. You need to control it yourself, e.g. resetting it yourself on only links with a (background) image since that's the major reason to reset it. But still, it breaks accessibility. Rather consider giving it a different outline color or style so that it is still visible, but less disturbing.
The font-size: 100% would force you to redefine them yourself in the <h1>, <h2>, etc elements. But even without the reset, you would often already like to do that anyway. What's the point of this reset then?
The vertical-align: baseline; breaks alignment of <sub> and <sup> so that they look like <small>. Further the table headers may also be affected. Those defaults to middle in all browsers. You would need to redefine them yourself again. Plus, it is known that this reset may cause IE6/7 to go havoc with images.
The value of background: transparent; is unclear to me. I don't see any point of this reset expect that it may make IE6/7 mad. You would also need to redefine the background color for all form input elements yourself again which just adds more work (for the case they're placed in a colored container). I am sure that whenever you encounter an element which needs transparent background, you could easily spot that yourself and set it yourself.
Enfin, see what you do with this information. I don't stop you from using the CSS reset. I myself have found the CSS reset only useful >10 years back when I was just starting with HTML/CSS. But with years and years, I've learnt as well that this is plain nonsense. But I admit, it's useful for starters since the reset will force them to set the margins and other stuff themselves explicitly. Which you could do as good without the reset.
