Levitra and Viagra are very similar except that Levitra begins to work a little sooner after administration.
The effects of Cialis last longer; up to 36 hours and studies show that men build up less resistance to Cialis with prolonged use than they do to Viagra.
These days generic viagra is the least expensive option with Cialis and Levitra being about twice the cost per useful dose. Bearing this in mind I don't know why anyone would use Levitra. Cialis has advantages that may justify the higher cost.