Headphone recommendations

Hey guys

I am a bit of a noob on headphones…but can someone clarify the difference between Audio Technia M50X and Audio Technica M50

Is the only difference the detachable cable? So I shouldn't bother paying $30 extra since there is no sound difference? How do the Audio Technica headphones compare to Logitech UE6000?

Also, how does Audio Technica process warranty claims?
If I buy from these stores, are the warranty process difficult to fulfil?

http://www.dwidigitalcameras.com.au/astore/Default.aspx
http://eglobaldigitalcameras.com.au

OR Ebay stores…

How difficult is it to obtain warranty claims?

I had a Beats Studio (got it as a gift) before and I only need to take photos of my damaged headphones and they sent me another one…. Is Audio Technica's Headphones convenient as well??

Thanks!