Extension tube question

Regarding extension tubes, I picked up a couple of short extension tubes when I bought a 6D last year (12mm, 20mm, 36mm). I'm thinking about playing around with macro photography a bit. I have 2 questions about the tubes.

The only fixed FL lenses I have right now are a 40MM STM (pancake) and the 50mm compact macro. Would the tubes work well on either of these?

I have a 6D and a 7D, which one would do macro better?

Certainly the tube set that you have would permit closer focus with both the 40mm and the 50mm lens. Since the 50mm macro lens was designed with appropriate optical corrections for subject distances much closer than 10x FL, it would be more likely to yield the best result, than if trying do the same thing with a lens never specifically designed for abberation corrections at very close distances, nor corrected to do 'flat field' photography. However, there is a lot of non-scientific and non-precision super-close focus photography which can be done even with lenses never designed for such close distances!

Also, in this day and age, the term 'macro' has devolved from being 'high magnification' photography (1X - 10X) to simply 'fill the frame with a small object many times larger than my frame'...CLOSE UP photography!

So, once again the 'It depends...' reply to a photographic question is appropriate to ask of the person posing the question, "...which one would do macro better?"

As for 6D vs. 7D, the difference is simply the ability to capture 24mm x 36mm image area, vs. the 15mm x 22.5mm image area...the optical considerations are identical, the magnification factor is identical