If they’ll end up on similar contracts (or contracts big enough to keep us out of any relevant FA talks), I gotta go with keeping Hayward. 
I mean, Smart deserves his 1st team all D but without reining him in, he could pretty much wreak havoc on your offense as well. If we can squeeze a friendlier team deal out of Hayward and then acquire a decent big for Marcus, I’d do it. 
I’d be sad (because Smart is entertaining to watch), but I’d probably do it.