I feel both of them are the same. It's our shallow knowledge that we diffrentiate.
1.'Om' the ultimate syllable and omkareshwar, lord shiva's name.
2. Sadashiva : one who has no beginning and no end.
this discussion is the result of someone trying to divide hindus, because the greatest of attained people whom we hardly get to see, are not vaishnav or shaivite, they just know god as pranav.
There is nothing such as insult to lord shiva because before aryans came, dravidians worshipped and knew only lord shiva. Are they the fallen race? no way..