FYI, Tadalafil has been around since 2003 (brand name Cialis).... a mere 5 years after Sildenafil was approved in the USA in 1998. In any case, it does not matter that Tadalafil has been around for 15 years as long as it works for the person taking it.
In my case, I have stocked both Tadalafil and sidenafil for different purposes. Tadalafil is known as the weekend drug here in the USA because it's positive effects last for around 36 hours, whereas Sildenafil is only effective for around 6 hours in my particular case. Initially I had terrible side effects with Tadalafil, which I managed to eliminate after reducing my dosage to 10mg and drinking enough water to keep myself hydrated. Works great now.
I prefer Sildenafil (25mg) when I know for sure that I am going to get action within the next 2 hours (for example a trip t0 NL ). Sildenafil gives me noticeably stronger erections and for some reason delays ejaculation too. No need to use any other drug for that purpose. From LK69's previous posts, it appears that it has the same affect on him as well.
As you noted, all of these work differently for every person. I am assuming you have tried various dosages of both these drugs. Sorry to hear that none of these work in your case. With your experience, I hope you will find an alternate method that works for you.
Cheers!