I am no expert but hgh is prescribed by doctors w/o slin. I have read a lot and it seems to me that w/o slin hgh still works darn good. It of course depends on your goals.
For gaining mass and strength I would say the added benefit of slin is quite noticeable.
For the effects of hgh, fat loss, feeling younger, better looking skin etc... I think hgh by itself is very good.