This a benchmark for different Ruby Libraries

rfeedparser: http://rfeedparser.rubyforge.org/
Syndication: http://syndication.rubyforge.org/doc/
SimpleRSS: http://simple-rss.rubyforge.org/
MagicRSS: http://github.com/astro/harvester/tree/master/mrss.rb

Feel free to run the benchmark on your computer to see/compare the results

Here is what I get for 1000 feeds (among the /feeds directory with my MBP 11/2008) and libxml (rfeedparser can make use of libxml or expat):

rfeedparser => Average: 0.491536916083916 (0 errors) RSS: 0.423777936991869 Atom: 0.557032825147347
syndication => Average: 0.0748718385155466 (4 errors) RSS: 0.058977287755102 Atom: 0.0902334358974358
simplerss => Average: 0.348966465534465 (0 errors) RSS: 0.158927489837398 Atom: 0.53265836345776
mrss => Average: 0.0573559627766599 (7 errors) RSS: 0.0519932346938776 Atom: 0.0625697261904762

With Expat :
mrss => Average: 0.0446699295774648 (7 errors) RSS: 0.0407380755102041 Atom: 0.0484925654761905
rfeedparser => Average: 0.396704025974026 (0 errors) RSS: 0.342670530487805 Atom: 0.448932866404715
syndication => Average: 0.0560052517552658 (4 errors) RSS: 0.0450482204081632 Atom: 0.0665948875739645
simplerss => Average: 0.279452683316683 (0 errors) RSS: 0.13230812195122 Atom: 0.421682789783891