OK, yes it's the same content, but the difference is Ice-T and NWA are more than just their lyrical content, they also have incredible mic skills, where as 50 doesn't. There's no way 50 could spit like Ice-T does on "New Jack Hustler", "Lethal Weapon", or "Hit The Deck", or many NWA songs, or have their energy. Him and many rappers today sound like they're half asleep and I hate that.
Plus Ice-T did more than make "I'm a gangsta" songs, he also described the downsides of that lifestyle.