I have used both and have to say the handy colibri wins for me,The fox pro has far too many sounds and at times can become a hindrance,when choosing which one to use.
the good thing about the fox pro is its distance,that it can be remotely used at ,anything upto 200 +.yards.goes through a fair few battery s 8 AA at a time and doesn't seem to last that long.
But for size and reliability,the little,colibri gets my vote,fits in your pocket has a good range of reliable calls and takes only 1 9v battery and it lasts a long time.