I would say that the Core i3 370M is going to give you the better performance, usally the Intel processors clock for clock outperform AMD, as well as the fact that the Intel is based off the 32nm process and the AMD is based off the 45nm process.
Im am 100% sure as I am not very familiar with mobile CPU's but I belive the Intel CPU also has more chache that the AMD which will help in performance, but also from a source I found also says the AMD consumes 25w and the Intel 35w. Im sure their are other opinions out there, but thats my 2cents.
Here are links to really the only comparison I could find of the two CPU's: Core i3 370M AMD Turion II P520
You have to scroll down to see them near the bottom of the list.