Recently, I've bought the micro2440 ARM9 board (WinCE or LINUX) to do my Project. My project is to build a login system with face detection and Authentication. And, I will use a usb webcam to do this project.
I think use which language is not important, c or c++ is all ok for arm9 system.
I just think that use arm9 to do this project is not very fixed.
Arm9 is mostly used as general cpu, not good at calculation.
For your project, there will be very big calculation.
So I think dsp is much better than arm.
Your project is very difficult, because you should need to develop a good arithmetic to implement face detection and authentication.
Good luck.