In my personal opinion, i would rather have the sweet than the imitation low carb stuff. Maybe have a little less of the "real" stuff. Obviously take insulin to cover it.
Also, I have found that for me, I don't need the whole candy bar. If I'm craving say, a snickers, one of the little fun sized ones usually satisfies me just fine. Now the trouble is just limiting yourself to one
Good luck! I am a big proponent of not excluding things from your diet, but instead just limiting them to "sometimes treats".