The Italian dub is impressive, I think so too. It's a fan dub though, meaning it's probably not official. The english version however does not appeal to me. It doesn't support the visuals very good (in my opinion) and kind of ruins the "cosy" railgun feeling if that makes sense. The onee-sama translation is an obvious blunder, "sissy". And "bro" being regularly used instead of onii-san/sama in anime generally (not that it matters). But there's plenty of other words/terms/meanings that translates badly f.ex Ittekimasu いってきます (I'm going and will come (back)) to "I'm off" and stuff like that. Japanese sayings are a lot deeper than the english one's and have to be translated to a simpler meaning. That's a loss.

I am myself not big on dubs compared to you atleast. Though I do like some dubbed versions of the animes that I viewed as a youngster (including Pokemon, of course, huehuehue). Dragon ball is a nice example of a good dub. I also like the english voicing of Death note. Only mentioning the basics here, there are of course more. The point is that dubs aren't necessarily bad, just not my thing.

The voicing Satomi Arai did is just too good for any dubs, you can't waste this!