Product review: Inside open source AJAX toolkits
Support: Online community
Nutshell: A lightweight tool built by a team focused on speed and quality
The most fun part of the MooTools experience may be choosing the plug-ins and functions you need before the server constructs the library for you directly. You add the desired functions (say, Accordian but not Smooth Scroller). The results can be compressed and delivered in five different ways, from full renaming of variables to just removing the comments to no compression at all.
MooTools is particularly proud of its speed, offering a benchmark for manipulating DOM elements that clearly shows it to be in the lead. Some Moo developers suggest that while other frameworks create small code, they work toward building fast code. A download that's 10 percent longer is only felt once, but a DOM search that's 10 percent slower is forever, or at least until the page is closed.
Moo code tends to be more object oriented, and the framework includes a number of functions for building and extending objects. You don't need to follow these leads or even include them in your custom-rolled version of the Moo library, but they're powerful, and they add a bit of simplicity for those who naturally think of data structures using object metaphors.
Many of the most popular constructions from the other libraries are also available here. You can chain together some of the effects just like jQuery, and there's an AJAX object for making an XMLHttpRequest call just like Prototype. The differences are important to some programmers, but they aren't too large.