Cialis is generally better, as it has a half-life of 36 hours. Unlike Viagra, it isn't affected by alcohol and food. Cialis is less potent, and best taken a couple of hours before sex. Cialis is good for men with genuine ED, because if you take it on a regular basis it gets stronger and stronger. Say sex every 3 days, and you've got the new Cialis in your system plus half of the one you took three days ago, and then 3 days later and another new one plus half of the one 3 days a go plus a bit of the one six days ago and so on. Once you get to this state you can have ad-hoc sex without planning and taking a tablet, because your body is ready all of the time. Just take one every 3 days and go with it.