[Capitan Totti]

So, I just got an iPhone 3G from a friend and it has iOS 4.1. Already jailbroke it and unlocked it, I like it but I am not gonna replace it over my BB for sure, however, I do want it to run as well as it can and I noticed that the phone has some issues. Now, I know its not a NEW phone so yes, battery will be a bit worn, and yes, its 412 Mhz and so I can't expect speeds of a 1Ghz+ CPU. But OMG, (did I just write that?), it takes like 8 to 10 seconds to open messages!? And like 10 to open Settings? Not to mention that when I go on Safari, the battery drops like crazy and I am on EDGE since I have T-Mobile.
So, I am wondering if switching to 3.1.3 from 4.1 will do any changes and I am here to ask pros and cons for those who know, especially when it comes to speed and battery. Which one would you say is the snappier iOS for the iPhone 3G? Thank you.