As stated by previous posters, Core-M CPU performance is quite comparable to the i7-620M if we look at micro benchmarks. In real life everyday applications, Core-M is likely to perform better because of its very quick power state switches and improved branch predictor.
As to the GPU performance, I'd like to wait for more game benchmarks. The Core M has around 2 times more computation power over the 330M, but I doubt that it will be able to make use of this advantage in games because of its limited TDP. Overall, I'd guess that 5300 will fare better in shader-intensive games while 330M should do better in games with simpler shaders and more overdraw.