The only difference between the i3-330UM and the i5-430UM is that the i5 has Turbo Boost. In basic use you'll probably see a small increase in performance because of this. If that is worth $75 then go for it.
The 5450 is a pretty weak graphics card. That being said, It's still an improvement over the integrated graphics and you should be able to run games on more demanding settings or with higher frame-rates when compared to the integrated graphics. Again, if that seems like it'd be worth the extra $50 then go for it.
Since these are mobility parts there aren't as many benchmarks out there so its hard to give you exact figures for what kind of performance increase you can expect.
I can tell you that I have a tm2t and I went with the i5-430 and the ATI Mobility 5450 Graphics card. I rarely use the Graphics card since it eats battery life but other than some minor complaints about the touch pad (get a mouse) and screen (the viewing angles are just terrible) I am extremely satisfied with it. For me its the perfect mash up between an Ipad and a lower end laptop.