A question I, and am sure many others have is "what about comparing the iso performance of RAW files to JPEG files, or the JPEG files using the multi frame noise reduction mode?". So let's see shall we?
|a familiar patch of grass|
I will be using the same setup as the previous test.
|Sony RX100 RAW ISO 3200 100% crop|
|Sony RX100 JPEG ISO 3200 100% crop|
|Sony RX100 MFNR ISO 3200 100% crop|
|Sony RX100 RAW ISO 6400 100% crop|
|Sony RX100 JPEG ISO 6400 100% crop|
|Sony RX100 MFNR ISO 6400 100% crop|
|Sony RX100 MFNR ISO 12800 100% crop|
|Sony RX100 MFNR ISO 25600 100% crop|
At iso 3200 there is not much difference between the normal JPEG and the MFNR file, so there is pretty much no reason to use MFNR at this iso. Your choice is probably between using the JPEG for convenience or the RAW for flexibility. With the RAW file you can achieve files as smooth as the JPEG easily by applying some noise reduction in post processing, but you also have the choice to retain more detail if you want, so the noise/detail tradeoff is in your hand.
At iso 6400 the difference between the JPEG and MFNR file is not massive, but certainly noticeable. They are both equally smooth but the MFNR file is able to retain more detail. The RAW file is almost able to match the MFNR file with post processing in terms of smoothness and detail, but again has far superior flexibility in terms of how much detail you want to sacrifice for smoothness. So at iso 6400 you have a choice between using the JPEG for maximum convenience, using RAW for maximum flexibility and quality, or in cases where there are no significant movements in the frame using MFNR for convenience and superior quality to the normal JPEG.
Of course if you ever need to use iso 12800 or 25600, you don't really have any choice but to use the multi frame noise reduction. But I must say that you shouldn't expect great quality photos at these two settings, as you can probably see yourself in the above samples. They will only look reasonable at small viewing sizes, maybe no more than 600x400 pixels. But I guess it's better to have the option available if you want than not at all.