The Celeron is the second least powerful processor that Intel makes, but for some people that is enough power. Most general purpose laptops these days come with an i3, and generally i5 and i7 are usually only used in workstations/gaming rigs. Xeons are server processors, Pentium and Celeron are budget processors.
Keeping this in view, which is better Celeron or i3?
Intel Celeron 847. The current comparison is one that did not actually need extensive testing or effort: the Intel Core i3 3217U is better than the Intel Celeron 847. Starting from the top, the i3 has the same amount of cores as the Celeron- two- but has a higher clock speed: 1.8GHz against the 1.1GHz of the Celeron.