The 3230M will be usefully-but-not-astonishingly faster if you're doing something that's CPU limited (like encoding.) But most of the time... meh.
Nah. In general use, you shouldn't notice a difference.
The i3-330M is a 2-core, 4-thread CPU with a 3MB cache. So are the 3317u and 3230m. So the only differences will be clock speed, turbo, and IPC improvements in the newer Ivy Bridge chips.
The 330m will be on par with the 3317u running at its baseline speed (1.7GHz) but once turbo comes into play, the newer CPUs will perform better. Except the clock speed advantages will be more noticeable in synthetic benchmarks than actual use, since the other components of the computers probably aren't appreciably different. (The older laptop might be limited to SATA-2 and USB 2, and the GPU is probably weak, but they're all going to be using dual channel DDR3, etc.)
BUT!
If you're I/O limited by a platter drive, you'll never notice the difference in light-medium use, web browsing, academic work, office type stuff, etc., because any CPU newer than an Atom will be spending too much time sitting on its thumbs.
The five things that make a computer awesome: I/O, I/O, I/O, I/O, and Compute.
If it were me? Sell the new laptop, get the 330m Dell back, drop in a 240GB SSD and max the RAM.