The N71 is almost like an enlarged version of the N61. A bit clunkier and unnecessary weight. As for the A52, the 5470 will provide less than satisfactory gaming performance. It's about on par with the desktop 4350. This card is at best, just an alternative to integrated graphics.
For the price range you're looking at, there really isn't anything better to offer from ASUS in terms of specifications. But if I had to choose, I would go with the N71 for the GT 325M. It has a slightly lower clock speed than the GT 320M, but it has a 50% shader count increase that should more than compensate.