Would Protoype and CI be slow?

[eluser]Nick Husher[/eluser]
What I mean is that if you go with jQuery or one of the other lightweight frameworks, you have less extensibility than YUI. Often, if you're trying to use a piece of code someone else wrote, you're stuck with how it works. You can modify their core files, but that can be problematic. Or you can put up with the problems with the imported code. Or you can write your own.

YUI's core libraries (and most of the major contributions) are massively exensible. You can layer your own desires and behaviors on top of the existing code very easily and you can take advantage of a lot of their "Provider" objects very easily.

I'm not sure I know in what sense of 'slow' you mean regarding YUI. As I said, YUI tends to be a bigger burden on your pipe, although there are plenty of ways to mitigate that (gzip compression, file minimization, combined requests, colocation, etc). For execution time, YUI is probably a little slower overall than jQuery, but most users won't notice the difference.

YUI Pageweights