I would go with Imagemagick since it is easier to code for. I see that they have convert, do they have any of the other applications, identify, mogrify, etc. ? Do you have shell access or do you have to use magickwand? I'm not familiar with it. Shell access is very easy, you just write a php script for it, it calls the BASH shell to run the script. You have a bit of learning to do, but you will be rewarded with a great deal of power over image processing. Imagemagick has a very good website.