Which comm. speaker mfgr. makes the best cabinet?

1) The Thiel cabinets. The cabinet fronts slope outward to improve timing and the fronts curve away to mitigate corner effects. They are very well braced and heavy to reduce flexing. Downsides: Passive radiator (doesn't bother me much most of the time but a lot of people are not crazy about that), terminals are hard to work with (you need to tilt the speaker up which requires a second person for the larger units), and you have to be careful about the relatively flimsy wood skirt at the bottom (don't use even a padded dolly on the larger units). They are attractive with excellent fit and finish.
2) The Montana cabinets are built like a brick &%@#house. Very, very heavy with a sextagonal (sp?)vs. rectangular design to help reduce standing waves. Woofers are moved outward from the tweeters in a less elegant fashion than the Thiels, but the effect is the same. Felt is used around the tweeters to reduce reflection effects. Did I mention that they are very, very heavy to reduce resonance? Their larger speakers have wheels for easy moving (at least on hardwood) and allow for spikes so the wheels can be lifted from the surface. Very easy access to terminals.

If you are considering cabinets that's are innert you would have to include Sony's top of the line. They are pyramid shaped and if my memory is correct Stereophile demonstrated little to no peaks in the cabinet throughout the frequency range. Now, I have never heard a pair, nor their super duper new variant but on this variable alone it is worth mentioning.

I wouldn't rule out Soliolquy..........

I love my Sonus Faber Extremas. They are a sealed unit for accuracy but have a radiator in the back to help with cabinet pressure.

They are slanted back a bit to help with the perceived phase distortion (timing errors between drivers) between the two drivers because of the different lengths in soundwaves of different frequencies. The two drivers are small and close together which also helps with phase distortion.

They are made out of wallnut on the outside which not only looks great but they claim it has also has an effect on sound quality.

I have also been told, but I have never seen, that the inside is shaped in a way to help break up or articulate certain frequencies.

And lastly the edges are smooth and rounded which help with reflection of the sound waves.

I read a book on speaker design and layed out all the options I would want in my custom speaker. The funny part was when I was done I noticed I had essentially designed the speaker I already own.

Now that I think about it Merlin's are innovative with there cabinet design. Those 3 lines in the front and on the top are brass I believe and run all the way through the speaker(there is some reason for this but I don't remember at this time), it is also made of some composite(not mdf) material; a mold if my memory serves me correct. Striked me as being a little weird for a high end manufacturer to do something like this.