OK, so it's more Railgun. But most of the series is taken up by the Sisters-arc, which is simply a re-telling of an arc we saw in the first Railgun series! But it's not like there was a 'universe reset', because we meet people that Misaka met in the first series... That's kind of confusing...
It is also jarring that there is such a big disconnect between the 'light side' of Academy City, where you have schoolkids doing normal, schoolkid-stuff, and the 'dark side' where there are experiments going on, people getting killed and all that. And of course there is quite a bit of escalation, because Misaka being one of the seven strongest ESPers in the city kinda precludes any meaningful opposition.
I liked the second arc of the series much, much better. It has a good mix between light and dark, and this time Misaka's friends get involved too, which makes for much more fun viewing. And since her friends aren't as powerful, the solutions they come up with are very entertaining and are different from "if it doesn't blow up the first time, simply apply more force".
Unfortunately, the second, more interesting, story arc is the shortest. Which makes the majority of the series just watching Misaka brood and then blow stuff up. It's not a bad series (though it does feature some uncomfortable scenes), so I'll give it a 7. But I think I'm done with both Index and Railgun by now -- it's becoming more of the same.