I actually enjoyed Scientific Railgun more than Magical Index because I thought the story and pacing was more consistent and I liked Mikoto as a character more. In general, I preferred the adventures of Mikoto and company rather than the magical side that Magical Index had. I honestly didn't really care for Touma or Index's character, either. Magical Index still had plenty of entertainment, but I love what Scientific Railgun brought to the table.
So yeah, I'm definitely excited for Railgun S and I hope that they make a third season of Magical Index sometime soon. Also, It'd be nice if Funimation could get the license of the second season and secure any further installments (I heard they're negotiating for the second season right now). Being able to see the Magical Index movie that just came out would be cool, too.