I haven't seen benchmarks of either to compare to be honest. I'm waiting until the 40nm tech hits graphics cards for laptops before I personally get a new one. Haven't had any trouble with the 3650 1gb in my laptop so far. I'd at least hope the 4650 runs better than that.
Yea the 4650 runs pretty well, but not as well as the GTX260M
here is a list for moblie graphics cards:http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html