The Celeron is a single core, single process CPU and according to Intel that Atom is a single core, dual process CPU (it has hyperthreading) ... however, that along with Atom's clock speed advantage still isn't enough to overcome that Celeron. If you want to know which is fastest, the Celeron. If you want to know which uses the least power and puts out the least heat? The Atom. Unless ultra long battery life is an absolute must, there are better alternatives out there for the uses you mentioned. You will be much, much happier with a lower-tier dual-core Pentium laptop than either of those two suggestions.