Hard to say. Personal preference is tough to gauge. If I was shopping for an 8 year old (again) I'd buy the Savage Cub-T (again). Just a terrific little rifle, with features far above the Cricket/Chipmunk rifles.
An 8 year old is probably still pretty small. There are "youth" sized rifles and then the very small type like the Cub, Mini-bolt, and the Crickets. For that age, for him to really be able to use and enjoy it, I'd stick with the smallest ones. The more common "youth" sizes are still quite a bit more than he's likely going to be able to support and manipulate well. My daughter is 9 now, and she's still not got the upper body strength to support the Cub for anything but rested and prone shooting. She's not a small kid for her age, but that rifle will fit her for the next 5 years at least, easily.