[Klaus]

RF 100mm f/2.8 L USM IS macro
https://cweb.canon.jp/eos/rf/lineup/rf100-f28l/image/spec/spec-mtf.png


RF 400mm f/2.8 L USM IS 
https://cweb.canon.jp/eos/rf/lineup/rf400-f28l/image/spec/spec-mtf.png

RF 600mm f/4 L USM IS
https://cweb.canon.jp/eos/rf/lineup/rf600-f4l/image/spec/spec-mtf.png

The 600mm is pretty much identical to the EF version. The 100mm/400mm are new designs.

The 400mm/600mm look as if they just attached an adapter actually.

[Brightcolours]

The 600mm is pretty much identical to the RF version. The 100mm/400mm are new designs.

The RF 600mm should indeed be identical to the RF version ;-)
But yes, the RF 600mm is optically identical to the EF version (EF 600mm f4 L IS USM III). The electronics, of course, are not.
Actually, the RF 400mm f2.8 IS USM is also "pretty much identical to the" EF version (EF 400mm f2.8 L IS USM III), optically. Again, the electronics are not, of course.
It is not strange that they chose to use the same optical designs, as both are top notch, very recent designs, and the shorter flange distance makes no difference with such tele prime lens design.

The 400mm/600mm look as if they just attached an adapter actually.

Indeed, which also makes sense (use the same barrel mouldings).

The RF 100mm f2.8 L Macro IS USM is (again) a pretty cool and interesting macro offering from Canon. Not only does it go to 1.4x magnification,
https://downloads.canon.com/nw/lens/rf100mm-f2.8lmacrousm/Mag.-1.4x-feature-1.gif
it also offers spherical aberration control (which some might remember from the Nikkor AF 135mm f2 DC and Nikkor AF 105mm f2 DC), to be able to adjust bokeh.
https://cweb.canon.jp/eos/rf/lineup/rf100-f28l/image/index/index-fig-03.jpg

[Rover]

The 400mm/600mm look as if they just attached an adapter actually.

Which is prolly exactly what they did. I theorized elsewhere that this is done with two subtle (and insidious) purposes: not only to sell basically the same lens to the users again, but also to prevent the adaptation to the different ML mount bodies, as now there are (smart) adapters from EF to just about any ML mount but none whatsoever from RF to anything.

Gah, my tinfoil hat's gone missing again!?

[Klaus]

I'm already curious to see how much more money they will ask for the "adapter". ;-)

[Brightcolours]

I'm already curious to see how much more money they will ask for the "adapter". ;-)

It is free.

[mst]

Yep, prices haven't changed compared to the EF versions. So, the question is, if there is any significant advantage in using the native RF lenses instead of the EF lenses with adapter?

[Brightcolours]

Some (like Klaus) object to the idea of using adapters (at least, where Canon cameras are concerned). That then is already one advantage, for that group.

Also, RF mount offers improved communications. "Along with a new microprocessor in the lens, the RF mount implements a 12-pin connection between the camera and the lens, a 50% increase over the 8 pins found on the EF mount. Along with more data channels, the new design provides higher speed data transfer for extremely fast AF, enhanced image stabilization and image quality optimization".
Also: "Within the lens a dual gyro sensor system detects any inadvertent physical movements of the system and this data is reported across lens-camera communication to the DIGIC 8 processor. At the same time the image sensor is “seeing” any blur stimulated by these same movements and it also reports this image data to the DIGIC 8 processor. These two data reports are algorithmically processed at very high speed and a compensation control signal is generated and sent back at high speed to the lens to actuate the IS optical element that counteracts the disturbance."

So, at least in theory, the native lenses, with their RF electronics, would be able to achieve AF faster and more precise and have better IS performance.

[Rover]

Yep, prices haven't changed compared to the EF versions. So, the question is, if there is any significant advantage in using the native RF lenses instead of the EF lenses with adapter?

It won't be "suddenly" discontinued (and rendered unserviceable) by Canon... at least not quite as soon.

[wim]

The 100 mm macro, as before, is not a 100 mm lens anymore when shooting macro. Focusing distance at 1:1 is 28 cm (object to sensor) and 26 cm at 1:1.4.

That means it is a 69 mm lens at 1x magnification and 65 mm lens at 1.4x magnification. This means I will certainly not get one.

For those who like to shoot video this behaviour may be beneficial, as it may have little to no focus breathing at normal shooting distances.

[Brightcolours]

The 100 mm macro, as before, is not a 100 mm lens anymore when shooting macro. Focusing distance at 1:1 is 28 cm (object to sensor) and 26 cm at 1:1.4.

That means it is a 69 mm lens at 1x magnification and 65 mm lens at 1.4x magnification. This means I will certainly not get one.

For those who like to shoot video this behaviour may be beneficial, as it may have little to no focus breathing at normal shooting distances.

Yeah.. about that.

You got those numbers from dpreview?
DPReview says 26cm MFD (1.4:1), 8.6cm working distance. 

The lens is internal focussing, as far as I know. 

DPReview says 28cm object distance at 1:1... So they gain 40% magnification with 2cm of movement (or to put it more clearly.... they gain 40% magnification with going only 7% closer to the subject)? And they say 11.2cm working distance at 1:1.
26 - 8.6 = 17.4cm
28 - 11.2 = 16.8cm.
Something is off with those DPReview numbers, and your calculations.

Canon states 26cm MFD and a lens length of 14.8cm. The RF mount has a 20mm flange distance. 26 - 14.8 - 2 = 9.2cm working distance instead of 8.6cm. So DPReview's working distance figure for MFD is wrong.

Can you point me/us to a Canon subject distance number for 1:1?

Anyway. You say you will not get one. You won't be getting the Canon EF 100mm f2.8 L USM then, either. It does 1:1 at 30cm MFD (this RF lens does 1.4:1 at 26cm MFD). Or the Canon EF 100mm f2.8 USM. It does 1:1  at 31cm MFD. Sigma's new 105mm f2.8 DN ART? 1:1 at 29.5cm MFD....