They are both very much alike. I am addicted to both, more so to crack though. I think they are both very addicting, and I would stick with sniffing it if I were you.. Once you start IV coke, you probably wont want to sniff it again though. That rush from IV coke, if it is good, is incredible, but its hard to space out the shots you are taking. If you can wait at least an hour between each shot you do, you will get a rush each time, but it still wont be as intense from going from baseline to coked up in one second, from that first one, the longer you space them out the better.
Crack is only as good as IV coke if you use the proper technique, there is way you need to hit it that makes it different than just smoking weed or something. I usually use a regular old glass straight stem with chore boy at the other end to put the hard onto, some people like to melt in on top of the brill or chore boy, before taking there hit, but I don't find it really helps, I just use the lowest heat possible, taking the lighter on and off the underside of the pipe where the crack sits, and is turned to oil/resin. Take a big enough hit to have a lung full of smoke/vapor, crack is actually vaporized when you smoke it... Try to have the pipe at an upward angle when you light it as I said with low heat, taking the flame on and off, don't leave it on the entire time, or you will vaporize it too quick. After the first touch with the lighter, usually right after you hear the crackling sound stop, start pointing the pipe at a downward angle, rotating it back and forth while moving it from an upward angle, to just straight, then downward, then bring it back up again to a straight upward angle toward the end of the hit. Try your hardest to hold the crack vapor in as long as possible, like 30 secs, then if it is good quality product, you will get an intense rush, sometimes better than IV coke IME, its all in your technique and the quality of each one.
In my case though being a user of both IV coke and smoking crack, again I will say they are much very alike.