Alien3 is more like the original Alien IMO, more of a horror movie than Aliens, which let's face it, it's not a horror, it's an action movie.
But to say that Alien3 is better than Aliens, well WTF have you been smoking Jim!
Aliens is about the best sci-fi movie ever made, it's held in the same regard as Bladerunner, Star Wars, Robocop, Predator, Terminator - Alien3 is not.
I like all the Alien movies, even Ressurection, but Aliens transcends it's own genre and stands on it's own as a great movie, Alien also stands on it's own as a great movie, Alien3 relies on Alien and Aliens to make any sort of impact. Visually it's great (sans the ropey 90's CGI), but it doesn't do anything that Bladerunner, Aliens, Predator etc didn't already do better - if you think about gritty sci-fi, you think Bladerunner or Mad Max, the future scenes in Terminator - nobody really thinks of Alien3, mostly because the CGI lets it down so much.
The prisoners are basically just the marines from Aliens with social issues. Ripley has to gain their trust, has to be almost raped, has to see some of them die... these are necessary plot vehicles. The point of Alien3 isn't that criminals can change, can stop raping people, or that people can change in general, the point of the prisoners was just like any non-Ripley character in any Alien movie, to die, so that Ripleys survival counts for more. If your names not Ripley, your cannon fodder, whether you survive or not, Ripley is the constant - you think that if they made an Aliens4, Winona Ryder would be playing the part of her semi-adopted robot daughter?, you think she'd be hanging out with Ron Perlman?, making wise-cracks over breakfast about her acid blood and questionable genetic makeup? You shouldn't get so attached to disposable commodities - but in any case, most people can probably tell you their favorite Aliens marine, but then ask them who their favorite rapist was from Alien3.
Let's be honest though, Ridley Scott took a huge steaming dump on the whole Aliens and vs Predator franchise with Permetheus. God, I hope he doesn't do the same to Bladerunner.