Please refer MATLAB help, Here i am giving some differences.
B = imresize(A, scale) returns image B that is scale times the size of A. The input image A can be a grayscale, RGB, or binary image. If scale is between 0 and 1.0, B is smaller than A. If scale is greater than 1.0, B is larger than A.
where as I = imcrop creates an interactive Crop Image tool associated with the image displayed. The Crop Image tool is a moveable, resizable rectangle that you can position interactively using the mouse.