You mention both the Slash and the Savage. Are you racing or just bashing? If you're just bashing and want a 4x4 off-road truck and the type (SCT, MT, electric, nitro, etc) doesn't factor in then the Savage is by far the most bulletproof truck there is. They are designed to take enormous amounts of punishment and is a proven sturdy design. I've had a couple and they are definitely the truck I'd hand to my 5yr old or anyone else to have fun with without any qualms.
Trust me, if you want to test a car to see if it will break, hand it to my 5yr old. He once managed to get a Savage stuck 5ft up IN A TREE with no jump or ramp. I have no idea how it happened, magic maybe.