I agree it somewhat depends on your needs and skills at getting the right exposure. However, there are some circumstances where it really does make a big difference. Such as the shoot I'm doing tonight, which is an inside dance/burlesque performance which will undoubtedly have some poor to really bad lighting. So RAW lets me push the exposure a bit and fix the white balance which is undoubtedly screwed up because multiple lights with different gels on them, and use what I believe is superior LR4 noise reduction as opposed to camera NR. I'll try out the Nik Dfine2 that I go through the Google Nik Collection deal.
So, long way of saying, I pretty much always shoot full-sized RAW with long exposure NR (which does darkslide exposure to subtract noise), and otherwise low or no in camera NR. And then after I sort through what I'm keeping, I delete the rest generally to save on storage space.
There was a period of time when I made myself shoot JPEG only because I thought to myself an excellent photographer must be able to get composition, exposure, color balance, and everything else perfect on the spot. The I was introduced to what LR4 could do and I became a convert to RAW shooting.
The reason I asked about size is because large RAW is just too big for storage. I don't know if small is high enough for printing wedding photo sized canvas, which I think is the largest print size I would ever need.
I heard that LR DNG format is smaller than CR2. I never convert format when I import. And I don't know if I should.
Hmm...well, I'd say it depends on the resolution of your S/M/Full RAW sizes. In general, S probably will give you most smaller print sizes. Take the resolution and divide by 300dpi to get how big a high quality print you can make.
Personally, the other use for full size RAW is if you find you need to crop to get framing/fix horizon/etc the extra resolution can be helpful. Then of course output at the size you need. You're right though, full sized RAW is very big, however my solution is to delete the ones that I decide are crap or aren't good enough to use. And then store them all on my ZFS NAS with CrashPlan backup.