Elena Vasquez is a urologist who long ago made peace with the fact that her most useful work often happens in slightly awkward conversations. Erectile dysfunction is common, treatable, and still wrapped in embarrassment, and she has spent her career making the subject ordinary so that people get seen rather than quietly giving up.
In the forum threads her habit is to find the one fact that actually matters in each question and lead with it. Across the whole PDE5 family the non-negotiable is nitrates, and she says so plainly every time it is relevant. She compares the three erection drugs without favourites, because the best one is the drug that fits your body, your other medicines and your life.
She covers the three PDE5 inhibitors here. As with everything on the site, her answers are general education from a doctor, not a treatment plan written for you.