There are countless options for self defense ammunition and EVERYONE has their opinion on what is best.
There are no absolute guarantees or solutions that will always be ideal. The best we can do is plan for the greatest number of possibilities and hope our planning fits some unforeseen need. If we could accurately predict the future we would simply always avoid danger.
I look at the problem as a game of Blackjack. While it's possible that I could be holding a hand of 19 and draw a 2, it's highly unlikely that I will draw a 2. Therefore, decisions in Blackjack (21) should be based on Probability not Possibility.
I see the selection of self-defense ammunition the same way. What has the highest probability of working as opposed to what might work.
I look for LONG track records of success.
While some exotic load might work extremely well and some well proven load might fail, I would rather take the more proven path. Call me overly cautious but I prefer to play good odds.
One of of those places where I look for long track records is the selection of self-defense ammunition for short barreled guns chambered in 38 Special.
I define "short barrel" as 2.5" or less.
Within that criteria, and addressing only factory loads for now, I see two factory loads with very long track records:
The "FBI Load" and the Speer Short Barrel load.
The "FBI Load" (a 158 grain SWC hollow point with a soft alloy and driven at +P pressures) has been with us since the early 1970's. It has a well documented history in both 4" barreled guns and short barreled guns.
The Speer Gold Dot 135 gr JHP +P "Short Barrel" load has been with us for well over 25 years.
Are there other options? - Sure
Could there be something available that is better? - Absolutely
Do new loads have longer track records? - NOPE