I'd probably have Cell winning, but I don't have any numbers to scale from right now. I generally see Teen Gohan and FP Cell being close in power, so I'd say Cell will be enough to beat Boo.
I take Cell by a hair, even though I do not like it. SPC is about equal to SSJ2 Kid Gohan, who Kaioshin thought would be enough to do the job against initial Fat Boo.
Well, Fat Boo was getting tossed around by Dabura, and Vegeta stated himself to be able to demolish Dabura. I'd give it to Cell, assuming it's revived him.