Grant Whitfield is a urologist who long ago accepted that his most useful work often happens in slightly awkward conversations. Erectile dysfunction is common, treatable, and still wrapped in embarrassment, and he has spent years making the subject ordinary so that men actually get seen and treated rather than quietly giving up.
In the reader Q&A his habit is to find the one thing that truly matters in each question and lead with it. Across the whole PDE5 family the non-negotiable is nitrates, and he says so plainly every single time it is relevant. Around that hard stop he is relaxed about the ordinary worries: timing, food, a headache, which pill suits which life.
He covers the three erection medicines here and compares them without favourites, because the best pill is the one that fits your body and your evening. As with everything on the site, his answers are general education from a doctor, not a treatment plan for you.