Sildenafil and tadalafil are the two most widely prescribed treatments for erectile dysfunction. Both help most men who try them, and both are now available as lower-cost generics. The question that matters is usually not which one is "better", but which one fits your routine.
Generic sildenafil is usually taken about an hour before sex and works for four to five hours. A heavy meal can delay the effect. Generic tadalafil, on the other hand, can work for up to 36 hours, and food makes little difference. Plenty of men also take a low daily dose of tadalafil so they do not have to plan ahead.
If you want a simple comparison, this guide walks through timing, food and side get more info effects.
A few safety points: never take either medicine with nitrate heart medicines or with "poppers". Let your doctor know about any other medicines you take. Common side effects are headache, flushing, a blocked nose and indigestion. Get urgent help for an erection lasting more than four hours or any sudden loss of sight or hearing.
Do not chase higher strengths. The licensed doses are 25, 50 or 100 mg for sildenafil and 2.5 to 20 mg for tadalafil. Bigger doses do not reliably work better, but they do make side effects more likely. Only take the dose your prescriber has set.
When you buy generic ED tablets online, check the strength on the pack and keep the leaflet. A valid prescription is required for every order of a prescription medicine. More practical tips are here.
This is general information, not medical advice. Always check with your doctor before starting a new medicine.