That seems like a pretty sweet price on an STI, and if you're not compromising your budget, I think the STI is quite a sexy car. I only have a bit of experience digging through details about each of the cars , but I really do like the STI even after being a hardcore Evo fan for years. (was looking at an Evo as well, but again, they're no longer being produced... really wanted that special edition Evo though, lol)
As someone who's completely out of the loop with respect to modding, I'd do some comparison there on your own. It's all about budget at the end of the day, and what you're able to spend. Not sure if maintenance will be any higher on the STI though. Good luck!