Both sildenafil and tadalafil are highly effective, and neither is “better” than the other. Depending on the person, they may or may not be effective.
Both sildenafil and tadalafil are effective and proven erectile dysfunction treatments. The active ingredient in Viagra is sildenafil, which is also available in a generic (non-branded) form.
The Cialis contains the active ingredient tadalafil, which is also available in a generic form.
While they both belong to the same drug class, PDE5 inhibitors, they differ slightly in some aspects, such as duration of action and side effects.