Comparing Festool's DOMINO to a dedicated Chisel and Bit Mortising Machine, the Leigh FMT/WoodRat. the Multi-Router and Horizontal Mortiser/Boring machines.
Rather than get into the pros and cons of "loose/floating tenon" vs "real" mortise and tenon joinery we'll limit this to just "loose/floating tenon" joinery.
Let's start by noting that the dedicated Chisels and Bit Mortising Machines aren't intended to cut mortises in end grain - a necessity with loose/floating tenon joinery. - for twop major reasons. First, because you're likely to split the wood. Second, the length of the part into which an end grain mortise is to be cut precludes getting the part under the chisel and bit - and holding it there while.
So, for loose/floating tenon M&T joinery we're looking at a jig and router set up - like the Leigh FMT, the WoodRat, theTREND M&T Jig and even the AKEDA jig - OR - a horizontal mortiser/boring machine with and XYZ table.
The router and jig units all basically work the same way - hold the part in the jig and move the router on the X,Y and Z axis. At a minimum, they require that you layout the Centerline and the End Points of the mortise, align the router to the centerline of the mortise and set "stops" to limit the cut to the end ponts of the mortise. Oh, and it's critical that the part you're mortising doesn't move while you cut the mortise. Did I mention that using one of these jig/router set ups don't do mortises in the ends of L O N G parts? OK soyou could stand on a ladder, or hang the part off the edge of a balcony or deck - but ......
Now to the Multi-Router - a router based horizontal mortiser/boring machine. You've got the same Centerline and End Points layouts to do - on at least one of each part - and bit to centerline alignment - and stops to set. But you HAVE the ability to cut mortises on the ends of L O N G parts, though the end may need supporting - and the support has to allow the part to move left/right and in/out WITHOUT moving Up/Down.
With the DOMINO there's no need for actual layout lines - all that can be done with pencil and paper - and the set up can be done with the "presets" built into the DOMINO.
All this text is probably getting boring - and too general. Some illustrations, with circles and arrows and notes would be nice - some specifics maybe?