Ok....It was late last night when I post previously....got some sleep...and thought some more...

Of course most RAW files are compressed!!!....the Canon crw, cr2...the Nikon nef, the Oly orf....etc, etc....they  ALL contain proprietary compression algorithms. Some are lossy, some are lossless.
So, their RAW file size is not indicative of the true amount of data captured by the sensor.

I thought though that Canon did have a feature to allow an UN-compressed file to be written to the card....perhaps some of the Canon guys can jump in here.  Some of the Nikons allow TIFF files to be written. The RAW format was developed to create a more efficient ( faster) way of writing data to the camera's card.

Regardless, point is...there is not "more" data with a noisy image....the amount of data captured is a function of the sensor.  The sensor captures the same amount of data regardless of scene (see my post in the sensor size/file size calc link above)...it is the compression algorithm (either JPG or RAW) that alters the file size.  "Similar" data sets allow for easier compression and more efficient file sizes.

@Kort...there really isn't more data...but the way the cam compresses that data into the RAW file determines the size...so, yes, a larger RAW file will take longer to write to the card.  If you wrote TIFF files to the card...the file sizes should all be "roughly" the same size.....although the write time would be painfully slow.  Again, do a test...convert your RAW files to TIFF...take a look at the bottom of your PS window.

In youth, we learn....with age, we understand.