Is there any major difference between the GT230M and GT250M?

I got a new laptop recently which has an nVidia GT230M graphics card in it which I was lead to believe would be decent enough to run most of my games in full. However, I just bought Just Cause 2 and as it turns out I had to turn down most of the graphics settings to get a stable framerate (although that is probably down to the sheer 400 sq. mile size of the game). Hypothetically speaking would a bit of extra beef in the graphics card cause too many problems with the computer? I was thinking of switching up to a GT250M notebook card because its in the same series as the current card, and it is 3D-gaming capable as well which I have tried out before and was well impressed by.

However, the current GT230M runs every other game I have in 1366x768 with full graphics at 60fps, with the exception of the recently-released Assassin's Creed II which runs at about 17-25fps on the same settings but is still well playable and doesn't lag at all graphically. So is it worth the time and money to get a new GT250M installed or not?

By the way the current specs for my laptop are as follows:

HP Pavilion DV6-2120TX

Intel i5 430M 2.27GHz (2.53GHz TurboBoost)

4GB of RAM

nVidia GT230M 1GB dedicated graphics card

500GB hard drive

Windows 7 Home Premium 32-bit