all 'should' work roughly the same, but 'roughly' ends up being a browser dependency...
I find that margin and padding work the best - did you mix "padding" with "marginpadding"? Images are an inline element when you get down to it, so they can easily be put side by side.
You can really go with either 'margin' or 'padding' for a little space between them if that's all you are shooting for. It's a
CSS Box Model issue, but unless you are using more than one feature of the box model, they might as well be the same. The difference between them really comes into play when you apply a border.
Just remember, that doing local CSS like that, it's done with the 'style' attirbute of <img so something like...
HTML Code:
<img src="myimage.jpg" style="margin:4px" />