I have tried both. Both have worked equally well, though I will have to say that Viagra does seem to last longer and have a sort of desensitizing quality that prolongs sex and prevents premature ejaculation, at least for me. I have also found that while I go with the full size 100 mg (a little white lie to the doctor) I can cut the pill in half or in quarters and it works just as well, which saves a lot of money. Unbelievable that Pfizer has been able to hold us hostage for this long, keeping their patent in legal limbo, thereby keeping us paying their prices.