GD2 or ImageMagick?

[waimichael]

I'm implementing the website which permits the users to upload their photos, create the thumbnails, resize and convert the format to jpeg on-the-fly, then stores them into file system. In my server, GD 2 and ImageMagick (not configure with PHP) are both installed. Would anyone have idea that which one is better to be used for the above functions?

Thanks.