I do not believe Rebellion runs significantly worse on most computers. A rare few say it either runs worse or better, but most say they get about the same performance as trinity. I also have 4GB RAM and an I-5, and while what I assume is Integrated graphics isn't a good thing, it shouldn't make the game unplayable, it just means you might have to turn off some of the new features like shadows.

I don't either, but I believe over thanksgiving I saw the best prices ever on both games, trinity being under $10 and Rebellion $13 some dollars. If you see those prices in a Christmas sale just get it, you won't see much better until next year.

Well given there was less than a $10 difference when it was on sale, it is absolutely worth the price. It's really the intended game for players new to the series. The new titans are really well done, and along with the new victory helps with one of the biggest complaints of Sins: games taking too long. The new subfactions, while I think could have been more distinct, are a welcome addition in that they bring some really different strategies to to the game. And you have all sorts of little things like the new maps, music and skyboxes that help the game stand out.

Also, if you are mainly looking at this game for single player (and it's probably how most people play the game), mods are a big deal (biased as I am its true). Diplomacy might have had more total due to being out longer, but the ones for Rebellion are clearly the best, and as time goes on I'm sure they'll be more of them too.

In a nutshell, get Rebellion, and if the price is an issue just pay close attention until a sale makes it cheap enough for you to get it.

Unless your current systems has major problems with your current Sins Version the game should run quite fine. Probably not on highest settings, but then what would you expect from an intergrated card.