My hubby and I used both. The difference for us was Zyban didn't work and Chantix did!
Zyban for me cause me to turn into a real B%#(%. I was set off any little thing and my hubby was deployed at the time so my daughter got the blunt of my lashings. The only good thing is it decreased my appitite and I did drop some weight! lol Wellbutrine is the same thing pretty much and it caused my sex drive to nose dive within a week of taking it and i felt worse on it too. Zyban for my hubby gave him a lot of sleepless nights. Neither one of us came close to stopping smoking on it either. We did it together but he was in Japan.
Chantix was the answer for us! We both did it at the same time (he was home this time) and we didn't even finish the whole first 6 weeks and we stopped smoking!! It made them taste and smell horrible to the point that you didn't want them at all!! A friend of ours smokes menthol ones and I would feel myself turn green when he came around just from the smell coming off his clothes!! YUCK!!! We will be smoke free 3 yrs this October!! Side effects for me- I had to take with food otherwise it felt like a small hot rock in my stomach and I would have dreams that I was driving back home going past a store there, seemed really real! And my hubby had none really. We were both on this before it got pulled off the market for a bit do to depression issue which we never experienced at all or any other irritability issues related to the pill or to the body not getting nicotine either. It was more the mind over matter. Getting in the car and not smoking, getting on the phone, with the fist cup of coffee, etc. You feel the urge but then remember how horrid it will taste and you just keep going with your day!
Good luck!! If you have any question, please ask! I see you haven't gotten too many responses from people that have used it first hand.