Well the big difference is as follows
Stealer of Souls once you get the combo going there is no response...I believe there's only like a few secrets that can actually fuck it up Oh My Yogg!, Explosive Runes, Potion of Polymorph, Counterspelland I think Pressure Plate but that involves you A. Having said secret in your deck (of those Oh My Yogg! is the only one that is actually played. Otherwise 9 times out of 10 you CAN'T respond you just have to watch helplessly as you die. This is like the old Butterfly Dagger Elma decks from back in the day.
Reno on the otherhand for a lot of situations IS the response...and these days barely a good one.