When the M5 came out Leica compared it to a classic body with a MR meter, it had cleaner lines and was not any bigger in volume, still 'compact' compared to the standard SLR body. And YES, there are 'advantages' to the M5 as I've said: the easy to adjust shutter speed dial, a rewind that really works well, finder information that gives more, and a really good semi-spot meter with an analog readout are the most useful to me. Almost forgot... the only M with both meter and self-timer which if your travelling makes it easy to get you and your friends in the picture.
Some users like how it balances with larger lenses and if you are using them the extra size of the M5 doesn't seem to matter. But I also like the camera with a compact 35 (pre-ASPH Summilux or Summicron), kind of equals out the lens/camera size.
When I carried around an ALPA 12 with the M5 it seemed even smaller still 😉