Cell uses 7 3.2ghz SPU core's and a single 3.2ghz CPU core.
360's Xenon uses 3 3.2ghz CPU' cores. SPE stand's for Synergistic Processing Unit.
Both are made by IBM.
Cell is much more powerful for gaming, as it's built closer to a graphic's card, where as 360 uses a standard CPU like one found in your PC, so it'd run Excel quite well. :P.
However the Cell is a bit harder to code for, so most developer's only use about 3 cores so it matches the 360 (for Cross-platform games), though some will use most of the cores, like Uncharted, Killzone n Final Fantasy XIII.
The current fastest Supercomputer IBM Roadrunner uses 12,000 Cell processor's to be the first computer to break the Petaflop barrier. And Toshiba sell add-on card's, like graphics cards, that use a single SPU core for video editing task's, because it's very fast at hard work. and they sell some DVD' players with SPU's in to uspcale DVD's to HD.