But that's just it, it just "feels" far leaner. jQuery, uncompressed and unminified, is almost as bulky as Prototype (100 KB vs. 124).
Prototype does a lot in that extra 24 KB, is faster on some benchmarks, and I just like the way the code looks. If you just minify and gzip Prototype, you're looking at a much lighter footprint.
In the end, none of the frameworks are very lean: though Mootools and YUI are at least modular.
That's not true though... jQuery, without any plugins, supports basic animation out-of-the-box (enough for the applications that I have been writing lately). Prototype requires scriptaculous on top of that if you want to write effects, which at a minimum is an additional 40kb for the effects module.
I know that prototype and scriptaculous provide more functionality, but my point is that jQuery is providing enough of what I need from both libraries while still being smaller.
Seriously though - I've written both and I'd find it hard to go wrong with either. jQuery is more the way I've been leaning of late, but were it to suddenly disappear off the face of the earth tomorrow I'd be fine with Prototype/Scriptaculous. To each, his own. :-)
Prototype does a lot in that extra 24 KB, is faster on some benchmarks, and I just like the way the code looks. If you just minify and gzip Prototype, you're looking at a much lighter footprint.
In the end, none of the frameworks are very lean: though Mootools and YUI are at least modular.