Return forwarding reference parameters - Best practice

In the following scenario

template <class T, class U>
? f(T&& a, U&& b)
{
    return a > b ? a : b; 
}

what would the optimum return type be ? My thoughts so far are :

1. Return by r value refs, perfectly forwarding the function arguments :

   template <class T, class U>
   decltype(auto) f(T&& a, U&& b)
   {
       return a > b ? forward<T>(a) : forward<U>(b); 
   }
   
   

2. Move construct the return value :

   template <class T, class U>
   auto f(T&& a, U&& b)
   {
       return a > b ? forward<T>(a) : forward<U>(b); 
   }
   
   

3. Try fo find a way to enable (N)RVOs (even though I think since I want to use the function arguments that's impossible)

Is there a problem with these solutions ? Is there a better one ? What's the best practice ?