[mjuhl24]

1. Most obviously, jQuery is completely encapsulated, whereas Prototype extends the DOM and pollutes the global namespace fairly rampantly.

2. jQuery is designed for ease of use. It is concise and understandable. Its learning curve is lower.

3. jQuery is becoming fairly ubiquitous. More people use it, which means more developers know it like the back of their hand.

4. The community, availability of plugins, extensions, tools, tutorials, and so on is much better for jQuery.

This is an outdated resource, but many of the facts still stand: http://ajaxian.com/archives/prototype-and-jquery-a-code-comp...