While my signature will show that I don't own any 9mm guns yet, I am fond of and familiar with the round. The 5-6 first-time gun owners I have helped purchase a home-defense pistol, practice with it, and choose ammo have all been steered toward the 9mm.
As their pistols tend to be 4" or longer in barrel length, I usually make sure they're supplied with a 147-grain JHP. Gold Dot, HST, and Winchester Ranger-T are my choices for defense ammo. Other brands like Remington Golden Saber and Winchester PDX1 are impressive, but to simplify my life I constantly find myself falling back on Gold Dot, HST, and Ranger-T - Proven, tested-and-retested rounds.
It's usually cold or windy in Wyoming, so heavy coats are common. I like the 147 for penetration. We're pretty physically fit, but we wear lots of layers.
In a smaller gun (3.5" barrel or shorter) I'd like Gold Dot, HST, or Ranger-T in 124 +p
I would not use a 115-grain JHP for defense. I would not trust the penetration.
For practice, whatever's cheap - and reasonable quality - you shouldn't need to wonder if your pistol or your ammo caused a failure. I have had flawless experiences with thousands of rounds of Winchester White Box and Federal Champion, but if I have the coin I prefer Federal American Eagle.
Beretta PX4; 92FS; 92S; 8040G | Sig Sauer SP2022; P6 | Colt Python 4"; 1968 Detective Special 2"| Smith & Wesson M642-1 | Ruger LCP; 10/22 | Daniel Defense M4V1 | Remington 870 | Alpine M1 Carbine | Steyr M1895 |1943 Izhevsk Mosin M91/30 | Walther PPS