Smoking was harder for me. A lot harder.
When I quit drinking, something had switched in me. I had a moment of clarity and realised that I hated who I was, my life, everything, and I had two options: give up on life or give up drinking. I chose to stop wallowing in my depression and get on with life. I won't say I found it easy from the beginning, because I didn't, but I didn't want to drink, because I associated drinking with the past and the past was something I didn't want to relive.
Quitting smoking, and staying stopped, was and is much harder for me. I have been sober for almost 10 months, and haven't had a cigarette in almost 6 months. I don't want to drink again, the thought repulses me. But smoking is a different story. I have to put far more effort into not smoking because not drinking has (aside from certain situations such as Christmas and holidays/parties etc) required pretty much no effort at all, it takes care of itself, because I want a sober life.
I want a smoke free life, too. I just see the consequences of smoking a cigarette being far less than drinking an alcoholic beverage, which makes it harder to stay stopped, I think.
Something only just occurred to me, actually. When I quit drinking I chose to 'do it alone' aside from SR, which I found 2 months after I quit anyway. I didn't need any support because, like I said, I had no desire to drink. I had to get support to stop smoking, though - I decided to make the most of the NHS here in England and have regular meetings with the nurse at my local surgery to chat about how things were going. I didn't feel 'helpless', I just felt that I needed someone to keep me accountable, and a reason for not smoking (they check the carbon monoxide levels in your lungs) besides just because it was bad for me...
For me, the fact that you can't see immediate effects with smoking made it HARDER to quit!