Oh, God, you guys are missing the best stuff in there...
The laser beam on all glass tubes is naturally round as a product of the round tube the gases are held in. RF tubes are square or rectangular and with help from special optics, produces an oval beam.
A round beam because the rube is round... but a square beam because the tube is square I'm going to start making square water hoses for grins and giggles.

Glass Tubes are excellent for cutting because they have a continuous beam instead of a beam that pulses on and off. You can cut Acrylic without having to flame polish the edges.
Yep, us RF-tube guys really hate our horrible acrylic cutting jobs... it just looks so ugly afterwards Thank heavens there are DC-tube users out there to bail us out else we'd be suffering.

When engraving, RF tubes do have an advantage over Glass Tubes because of the pulse technology and the shadings of photographs. This advantage is short lived, however, because the photo softwares out there can convert an image to a bitmap that optimizes the photo for engraving and turns it into a series of dots that make the laser turn on and off when engraving the photograph.
We must create such horrible engravings with our RF tubes because of those square dots we're forced to make instead of the DC's smoother round dots...

I could go on and on...

But why would you buy an expensive piece of equipment from a vendor who is obviously completely clueless about their own product? It almost has the feel of an April Fool's joke... almost.