The Nvidia GeForce GT 230M and 240M are becoming quite popular in mainstream and multimedia laptops, while the GTS 250M is being introduced in high-end and gaming laptops. So I think it’s interesting to have a look at the available benchmarks (mainly from Notebookjournal.de and Notebookcheck).
The GT 230M and 240M perform quite similarly, giving enough performance in most games at low resolutions and medium or high settings. The GT 240M gives 10-20% more performance than the 230M. The problem is that the good ATI Mobility Radeon HD 4650 is faster than the GT 240M, sometimes by a good margin. Of course both are faster than the ATI Mobility Radeon HD 4570. The GT 230M is used in many HP Pavilion laptops, such as the dv6t Quad 
, dv7t Quad
and dv8t (UK link).
The GTS 250M could look like a gaming card because of the GTS prefix, but in many cases its performance is way lower than that of the GTX 260M, specially at high resolutions, and in many cases it’s closer to the one of the ATI Mobility Radeon HD 4670. The GTS 250M is often found in Core i7 laptops.
At the end of the day, the decision is going to depend a lot on pricing and the actual games you play, but generally speaking:
GTX 260M >> GTS 250M > HD 4670 > HD 4650 > GT 240M > GT 230M > GT 220M >> HD 4570
Main sources: GT 240M benchmarks at Notebookjournal.de, GTS 250M benchmarks at Notebookjournal.de
See also the benchmarks at Notebookcheck (go to the bottom of the page):
