I like Sharon more, however i have only tested IH for short in SL so far but didn't found him that great like everyone says.
Also it seems Sharon gets a new uniform with the next update, so maybe more power to her ;-)
Far from a master so take this with a grain of salt.
I don't have them on equal footing for a direct comparison, but I have preferred Iron Hammer over Sharog. Universal is handy too. Honestly you probably can't go wrong with either so I wouldn't stress it.
I know Anti-Venom is considered a must have (just bought it myself) as hes apparently the best WBU striker. If not that, I think most people would say IW cap.