These in fact compile to the same assembly:
NSNumber *value = @42;
NSNumber *otherValue = @(42);
This leads to the following optimized assembly:
// NSNumber *value = @42;
movl L_OBJC_CLASSLIST_REFERENCES_$_-L0$pb(%edi), %eax <-- NSNumber
movl L_OBJC_SELECTOR_REFERENCES_-L0$pb(%edi), %ecx <-- numberWithInt:
movl %ecx, 4(%esp)
movl %eax, (%esp)
movl $42, 8(%esp) <-- Here's your value
calll L_objc_msgSend$stub
// NSNumber *value = @(42);
movl L_OBJC_CLASSLIST_REFERENCES_$_-L0$pb(%edi), %eax <-- NSNumber
movl L_OBJC_SELECTOR_REFERENCES_-L0$pb(%edi), %ecx <-- numberWithInt:
movl %ecx, 4(%esp)
movl %eax, (%esp)
movl $42, 8(%esp) <--- and here again
calll L_objc_msgSend$stub
It's worth noting that it's even smart enough to do pre-computing for you:
// NSNumber *value = @(42 + 1);
movl L_OBJC_CLASSLIST_REFERENCES_$_-L0$pb(%edi), %eax <-- NSNumber
movl L_OBJC_SELECTOR_REFERENCES_-L0$pb(%edi), %ecx <-- numberWithInt:
movl %ecx, 4(%esp)
movl %eax, (%esp)
movl $43, 8(%esp) <--- Hey; it's precomputed to 43. Nice.
calll L_objc_msgSend$stub
So as @Zaph says, it doesn't matter to the compiler.