Mirka's sanders are in my opinion the only tools made to date that are dedicated fully to using mesh abrasives.
Yes, I know you can slap mesh on just about any sander on the market, but the differences are in the backing pads, not the abrasives. All alternatives have fewer, larger extraction & "air bleed" holes that are predicated to paper backed abrasives, not mesh. This is the principle reason that Mirka's extraction is so effective in comparison to others.
As for "comparing" Mirka to Festo/ol, I can only comment that they're different. Mirkas are lighter, but are available in a smaller range too. Festool offer more expensive & cheaper alternatives. M's sanders are significantly lighter, have superior extraction (particularly of fines such as gypsum dust), & in my opinion are ergonomically superior.
In Randos, the DEROS sanders are available in 77mm, 125/150mm & 150mm. Available in 2.5mm, 5.0mm & (in 150mm only) 8.0mm orbits. Most, if not all Mirkas are available in a pretty Bumble-Bee Black & Gold Systainer or cardboard, as preferred.
Much of the range has been awarded the Red Dot Industrial Design award: LEROS, DEROS & AOS.
In terms of design, much of Mirka's range has paddle-switch actuation in a similar manner to air sanders. This has both advantages & disadvantages. I usually program the tool to use the paddle as an on/off switch (rather than a variable speed control) & temporarily tape the paddle "on" with a few inches of insulation tape to allow me to frequently alter my handgrip.
Personally, the approx 20-25% savings in both weight & price, plus the superior ergonomics & extraction makes Mirka's device simply "a better mousetrap".
Anecdotally, there have been some issues with reliability of the "plug-it" type cable connectors with both F/tool & Mirka's sanders. There have also been some reports of the sealed EC motor unit failing in Mirka's sanders. I've had 5 Mirka sanders (2 DEOS, 2 DEROS & a Delmeq DEOS "clone") with nary a hint of any problem or issue. M offers a similar 3 year product Registration-dependent warranty to F/tool.
Mirka also makes/manufactures & supplies parts for a whole swag of manufacturers with a complete kaleidoscope of colours available from not only Mirka, but also Metabo, Delmeq, Rupes, Car System, Indasa, Sumake, Menzer & Pela Tools. Some are less than 1/2 the price of an "original" Mirka (or 60-70% less than the price of the EC F/tool)! Most of them also eschew those stupid Plug-It type power cables too, which is in my opinion a bonus. Additionally, all consumables (pads, abrasives, interfaces & pad protectors, even motors & many body-parts) are interchangeable between the clones too.
On a personal level I've actually replaced almost all (7 actually) of my old F/tool sanders (I've kept an old BS105E Belt sander kit) with 3 Mirkas & a Delmeq.