I use a macro lens for "normal" close-up, a reversing ring or bellows/extension (usually on a 35mm or 50mm lens) for "closer" macro work, and a combination of a reversed lens with extension for "ultra" macro work.
The amount of extension needed is directly proportional to the focal length. Longer lenses (MF lenses are longer) thus need more extension than shorter lenses (like the ones used on 35 mm cameras and the even shorter ones used on sub-35 mm format digital sensor cameras) to reach the same degree of magnification.
Also, 35 mm format lenses are smaller, and fancy tricks, like not just using extension to reach a certain degree of magnification, but changing the focal length of the lens while focussing as well, are a lot cheaper then they would be if the lens would have to cover a larger format.
MF lenses are larger, thus put more weight on the focussing helicoid. This sets a mechanical limit to how far you can rack tsuch a thing out before it will start to sag under the strain.
So you will need rigid extension tubes sooner with larger formats than with smaller formats.
Now if all you want to record are three teeth at 1:1, and these fit inside a 35 mm frame, there is absolutely no reason to use a larger format. All you will get is more of what is next to the teeth, more of what you were not interested in.
If you want to photograph the same three teeth, but at a higher magnification, so the fill the larger 6x7 frame the same as they do the 35 mm frame, you will need a bigger, more cumbersome kit.
View camera's movements do offer advantages, because you can position the plane of focus more or less where you like. It is not necessary (as in cameras without movements) to have it paralel to the film plane. Can be of very great help to get more of the image in focus (and/or in depth of field).
Iagree. I was aware of movements from my view camera work when I got my Nikon bellows, which offer limited movements.T hey are still a big help!
I have a British 'BPM' Bellows unit with both PENTAX M42 and CANON FD flanges on it -- I use it a lot with my 105mm f4.5 E-Rokkor enlarging lens and it gives good results. When I got my 6x7 outfit in November 1980 I also got teh extension tube set and found it useful, then in about 2003 I got a 6x7 Mk II very cheap with the 135mm f4 SMC Macro-Takumar and found I needed a tube to get really close but the depth of field was very small due to the film size -- here is my Spotmatic with the bellows unit -- PentaxBellows by pentaxpete, on Flickr