Yes there are some subtle changes, but why subtle. There should be some major changes, since I'm changing from stock to hi-fi earphones and also M1 are 4x the price of Samsung's stock. If there are changes then why I need to listen intently, I should notice them as I listen. But I don't feel that I'm listening anything hi-fi earphones.
There are some changes like highs in stock are overpowering, comfort and build quality is not as good as M1. But still my expectations was high from M1.
Here is a thread, which has a discussion related to my problem, there are many users feeling the same way so I'm not the only one.
I will compare them more, but many said in forums that M1 is much better than ep-630. Don't know when I get this feeling. :(
Audio, especially high-end audio, is all about subtle changes. If you don't care enough for listen to them then there's simply no need to go beyond entry-level. Enhanced bass is popular in the mainstream for a reason - differences there are very easy to hear. Going beyond that takes time - give yourself a few weeks with just the M1 without going back to your other sets and the differences will be more obvious when you switch back. After that you can decide if you want to keep them or not. Also, there are some stock buds that really aren't bad - luck of the draw there - and there are probably quite a few tracks that don't really benefit much from the strengths of the M1. If you're listening to dynamically-compressed pop in 128kbps mp3, you'll hear less of a difference than someone listening to a good recording might.
Depends on whether you like their sound signature.