Would Protoype and CI be slow?

[eluser]peterbz[/eluser]
[quote author="Nick Husher" date="1228420062"]It's been my experience that with other libraries, you either have to use the stuff made by others or roll your own from the ground up. YUI is based heavily on a modular extension model, so you can create a subclass of one of the existing UI objects and build off of their platform. Or, you can use one of their provider objects to make it easier to manage object configuration, event handling, etc.[/quote]
By using stuff made by others, are you referring to something like scriptalicious for Prototype?

Also, is YUI slow compared to jQuery UI? I want something that would provide very nice UI enhancements without much hassle but at the same time leave behind as small of footprint as possible.