Afraid a Celeron isn't very competitive with an i5, even at the same speed. At least not comparing to similarly clocked computers running here. A dual-core Celeron based PC here is significantly slower than a similarly clocked i5 Mac Mini.
Oh interesting. The desktop I was referring to has a 4 year old Celeron at 1.9Ghz, so possibly its older architecture makes it more different, but not sure.