If your going as far as 25K, i woudn't think twice about which to pick, it would definitely be a 330Ci
I have driven a friend's 2002 330ci, and quite frankly its the best car i've had the privelage of driving. Mind you, you will need to be a bit "computer bounded" , because theres more to it than just the driving and shifting, you got buttons all over the place that will drive you up the wall (metaphor :P )
The 325ci is simply smaller in engine size, and less "bulky" ...I think you know what I mean, you can see the 330ci is like the M3 , and looks like it floats over potholes and bumps - (which it virtually does)
Just take your time, remember its a lot of money, so make sure you throw it somewhere that will make you happy.