Guys i have 2 images one with CMYK color model and other with sRGB.. I would like to find out which color model is better to use while dealing with image processing like resizing, cropping, color filling etc.. Thanks in advance guys.. !
CMYK color space is used for print, (s)RGB is used for screens (web, monitors, tvs etc). If one were to open a CMYK document in a viewer/program that doesn't support the color profile (which is not uncommon, since CMYK isn't as widely supported as RBG) the colors would appear to be extremely over-saturated. If you are altering the images for use on the web, or in an application, I would highly recommend that you use some variant of RGB.
In short, neither is really better than the other in general, it all depends on where you will be using the images (apples and oranges, comes to mind). CMYK is better for print, and (s)RGB is better for screens.
UPDATE in response to OP's comment:
Just to be clear (forgive me if you already know this) color space/profiles do not affect the resolution of an image, they only affect how the colors are handled/encoded. Resolution is only affected by file dimensions, DPI/PPI (dots/pixels per inch) and compression.
UPDATE 2 in response to OP's comment:
I'm not familiar with "Imagemagick", but in general, I can tell you that I've converted thousands of documents to RGB from CMYK (and vise versa) and never noticed any degradation in quality, when the file is viewed in a program that supports the color profile. The only exception is when converting to CMYK FROM RGB, it is possible to lose a wee bit of vibrancy (due to the fact that CMYK is a smaller color space. Like I said before, if by "quality" you mean "resolution" the color profile won't effect it, the image won't suddenly lose clarity, when switching color profiles. Let me know if you have any other questions.