For some reason I havent bothered to dig into, the high-ISO RAW shots from my 600D are significantly noisier than the Jpegs (in-camera long shutter noise reduction enabled for JPEGs). A cursory glance showed me no significant easily visible advantage that the RAW had over JPEGs in this particular case (High ISO, longer shutter open periods). On the contrary if I can get a JPEG that looks better than the corresponding RAW, I have no real reason ATM to switch to RAW and then use PP to get rid of the noise. The noise was of the chroma type and it was significant.
As izzikio_rage said, the reason for this is the extensive post-processing that happens in camera. And again as he said (I seem to agree with him a lot) it makes more sense to decide the post processing parameters yourself rather than let the camera decide for you. If you don't want to start from scratch there is a very easy workaround for DPP users. Load the RAW image in DPP, the use the picture style option to choose whichever picture style you would have used in camera and you immediately get the RAW file processed exactly like the JPEG in your camera. You can now use this as a starting point to tweak the file further, with all the latitude that RAW allows.
Also raw files generally have a lot more color depth, 12bits compared to the 8 of a jpeg (will confirm the numbers), all that info is lost by the cam if a jpeg is made. And it can make all the difference when shooting a scene with a high range.
And I agree with him (again). I very often find myself hitting the limits of JPEG bit depth. I'm surprised that others aren't as frustrated as I am working with JPEGs.
maybe I will just create a RAW conversion profile and use it for every pic ...which will be similar to jpeg conversion by DSLR.
Only if you set up a JPEG profile in your camera that is perfect for the shooting conditions. If not, getting the RAW settings just right in one file and running a batch process with that recipe on a bunch of files will yield significantly differnt results to out-of-camera JPEGs.
For this reason alone I shoot in RAW+jpeg format so that I have to process only those I desire for the rest jpegs would doo .
The RAW files have a JPEG file embedded in them so RAW+JPEG is a bit redundant unless you have a burning need to send the files out directly after shooting, like being the first to upload your pics to Facebook or something like that.
and burst speed will reduce
I suspect that is to do with the speed of the memory card. The burst slows because the buffer is full.