Some reality is needed here.
In 4 seasons, Jeff Green has shot more three pointers than Josh Smith has in 8 seasons. Sure he makes them at a bit better rate, but not nearly enough to be worth twice the three pointers a season. They have almost identical TS% and eFG%, neither of which is all that good. Smith is a 50% better rebounder, a 50% better steal generator, an almost double passer, and a better than 3 times better shot blocker. Even the USG% is a lot closer than one would think.
Josh Smith is a significantly better player than Jeff Green was and that was before Jeff Green missed an entire season with a heart related medical condition. And Smith is only a year older so age isn't a factor, where it is in other situations.
The only reasons to choose Jeff Green over Josh Smith are Green is a free agent and Smith is not (thus to get Smith you probably have to give up value) and Green will likely cost a fair amount less financially than Smith (though who knows what Green will want going forward).