I'd just buy a 2nd hand one myself with a bunch of games.
Even for a present, if it's still boxed it will probably look as good as new. If the kid is young, they won't know, or won't care because of all the games. If they are older, just ask them if they would mind a 2nd hand one with loads of games + the rest of the money you saved spent on something else.
Either way, I'm sure they wouldn't care.
When looking at a product and looking at new vs used I decided based on how a product is 'used'. A console sits there on a shelf and gets 1 or 2 buttons pressed on it now and then. So it's not really 'used' in the same sense as say and item of clothing.
Buy a NEW controller - that's the only part that wears visually really. I sold a PS3 few months back and other than controller it looked as good as the day I bought it.
Everyone I know with Slims have had then in use 20-30 hours a week for 5-6 years with no issues.