http://www.techarp.com/showarticle.aspx?artno=98&pgno=0
Mobility Radeon HD 3650:
Architecture: M86
Fabrication Process: 0.055 Micron
Transistor count: 387 million
Directx: 10.1
Power Management: PowerPlay 7.0
Vertex Shaders: 120
Vertex Shader Version: 4.1
ROPs: 4
Textures/Clock: 8
Pixel Shaders: 120
Pixel Shader Version: 4.1
Core Speed: 550MHz
Fill Rate: 4400MTexeles/sec
Memory Bus Width: 128 bits
Memory Type: DDR2 or GDDR3
Memory Speed: 400 or 800 MHz
Memory Bandwidth: 12.8 GB/s or 25.6 GB/s
I'm guessing this uses system memory and also has some GDDR3 memory of its own, you just need to compare how much with the other.
Geforce 9600M: There's a GS and a GT version. I'll note if theres any difference between them.
Architecture: G96M
Fabrication Process: 0.065 Micron
Transistory count: NA
DirectX: 10
Power Management: PowerMizer 7.0
Vertex Shaders: 32
Vertex Shader Version: 4.0
ROPs: NA
Textures/Clock: 16
Pixel Shaders: 32
Pixel Shader Version: 4.0
Core Speed:
GS: 430 MHz/860 MHz shaders
GT: 500 MHZ/1250 MHz shaders
Fill Rate:
GS: 6880 MTexels/s
GT: 8000 MTexels/s
Memory Bus Width: NA
Memory Type: NA
Memory Speed: NA
Memory Bandwidth: NA
You can't really compare Vertex and Pixel Shaders because one of them uses "units" while the other uses "cores". The 3650 has some of its own high-performance GDDR3 memory and can use system memory if that is taken up while the 9600M has to use system memory only. The 9600M has slightly better specs than the 3650 but because it doesn't have any GDDR3 memory, the 3650 will outperform it.
The aspire has the 9600M GS which is the worse version so I'm assuming the satellite has the HD 3650 and therefore you picked the right one =). I haven't been a fan of the Acer brand because they used to be emachines and I view them as a bargain basement brand. My friend has a Toshiba and hes never had any problems with it so I think you made the right choice.