psm1

hi guys ,

I' m a french software seller, and i'd like to pass PSM1, that will surely help me in the dialogue with my team of developpers )

To begin , i've seen that there were also a CSM certification , which seems to be more "superficial"
So , can you tell me teh difference between these two certifications . Is it better to pass both , start with CSM.?

By the way , i allow myself another question , what do you think about web site test like "testtaker.."? Do you know other webisite like this?

Thanks for you help

Regards.