why is it that the Speer Gold Dots are so highly recommended? ...
... what is it that sets them apart from all these other brands?
Part of it is that they're a proven design and not over-hyped, and come at a price point that you can do your own reliability / expansion testing in your own gun.
No ammo is reliable until you test it in your gun(s) yourself.
That said, I like Gold Dots because they feed in
everything I own, even my oldest gun (A Walther P.1 from 1979 that doesn't like
anything but steel-case or Winchester white box ball ammo, I actually keep a box of standard pressure Gold Dots around just for that gun).
I buy +P for any gun that's rated for it, and do my testing for feeding and blow up some water jugs with it, then I only shoot the stuff to expend old carry ammo, mostly I shoot cheap standard pressure stuff for range time.
+P is generally not going to make a huge difference in terminal ballistics, unless the HP design is marginal and needs a bit more speed to expand well ... basically +P is wringing the last 5-10% of performance out of a platform at the cost of some longevity, load up with standard pressure if you like so long as it runs well in your chosen defensive gun
You've already solved
step 1 - have a gun
I assume you've solved
step 2 - know how to use it
So don't stress out about
step 87 - pick the perfect defensive ammo
It is nowhere near as important as
step 0 - don't panic