Viagara gives you 4 hours top "hard on" if you are shagging with your beau, SP or "civilian". Pfizer creates the ED category and the company still have relative strong franchise cause since 98, they can pretty what you expect.
Cialis gives you max. 36 hours "hard on" if you want to, plus you don't have to wait your Mr. Happy to stand and walk tall. It's just right the way. Obviously Bayer and Eli Lilly are quite successful of stealing the market by discounts and massive commerical promotion, more subtle than say Levitra or Viagara.
However, it's still relatively new and we don't know how long will it takes to sort out all the strength and weakness of the pill. Time will tell but don't count on Pfizer giving up the leadership that easy.
Levitra from Glaxo shows no significant difference compared to the blue pill. That's why they resort ok early middle-aged Brunette to seduce horny guys at the commercials.
BTW, don't ever tell you mate, especially "civilian" one you just take either pill, they will probably say, "Oh No, not again!". I suspect many women see all those ED thing as nothing but money grabbing by Big Pharma and commerical glimick, especially the Levitra ads.
Don't be surprised when many of those women thank God for stopping those guys getting hard on-horny and ask for sex.
Sigh....maybe I need one of those pills to make Mr. Happy a stud to make sure the SP or worse "civilian" chicks won't make fun on me