I think that while it's got a lot to do with preference it has more to do with how you started. I was introduced to violin without the shoulder rest and I find it more comfortable to play without one. Though I keep a Kun Bravo just in case I'm ever very uncomfortable or in the mood to not strain my neck and shoulder too much. I've found that it disrupts my natural flow whilst playing, but that's just me.

But to answer the question, as has been said I don't think a shoulder rest is going to disrupt or absorb any more sound than your bare shoulder would.

Shoulder rest for me is essential. Since I was in elementary, I have difficulty playing the violin. I cannot tuck the violin under my chin very well and sometimes it would slip as I cannot shift my fingers well. Not until someone lent me her shoulder rest and which helped me play well. Though I knew it limited the sounds that I produced. But everytime I would go to play the violin even just to practice, I can't stand without my shoulder rest especially with pieces having lots of shiftings. But now I'm trying to work it out not to use shoulder rest, even though it's hard for me.
Could you please give me some advice? How much would it affect my playing?

Sponge + Rubberband = Gay!

I have a Kun, it was $40. Worth Every penny. However it was like 1/4 the actual cost of my Violin. lol. Having said that, I'm pleased with it, it's a nice little instrument. I even currently am working on a Minuet for a Violin.

I don't see why people make such a great deal about using shoulder-rests when obviously it's not doing anyone any good. I mean, if you compare the greats of today - Shaham, Vengerov, Mutter, Chung, Hahn - with those of yesterday - Heifetz, Menuhin, Oistrakh, Milstein, Neveu, et al. - I think many will find that yesterday's violinists were 1) generally far greater in technique, and 2) far more diverse than today's can ever hope to be. I think that a teacher's saying that one has to use a shoulder rest to play the violin/viola is both a ridiculous suggestion considering the above statements and an attempt to mass-produce students who all sound like the teacher, and are not really allowed to experiment, like yesterday's violinists were allowed to do a lot.

__________________
"Aufersteh'n, ja aufersteh'n
wirst du, mein Herz, in einem Nu!
Was du geschlagen
zu Gott wird es dich tragen!"
-Gustav Mahler