Ask YC: What tool to build a web widget

Hi. I am debating what the best way to build a web widget is. Two methods I am thinking are as follows: 1. Create a page on my site and use an iFrame code with the link to that page. 2. Create a javascript code and use a script with the link to the javascript.

Is there really a difference? Which do you like more? I see Flash is another option, but I would want to avoid it. Any other options?