I have a hollow chisel mortiser I will probably sell at some point, a Jet, and a Domino XL. If you get the smaller domino, you are limited to mortises about an inch deep and 8 or 10 mm (can't remember which) wide. The XL will cut mortises about 2 3/4 deep by as much as 14mm wide. With an adapter, I also use the little bits for the smaller domino. I like to build big as well as little things and I thus think the smaller domino is just too small for me. I am happy with the bigger one but it, of course, costs more. You can save a bit using CMT cutters (the XL comes only with a 12mm). So I bought CMT 14mm, 10mm, 8mm, 6mm, and 5mm. I could get a 4mm but have seen no need so far. They work fine. The 5 and 6 require the Senica adapter.
A benchtop mortiser like my Jet produces fine mortises and can go about as deep as the XL domino. But the sides of the mortise are rougher which is not terribly important. It cannot reasonably be used to cut mortises in long pieces like the domino does easily. It also takes up more space and takes longer to set up. It is also fussier in use. If I do not lube the drill bit a little it gets hot and if I lube it too much it gets on the project. My domino lives on a shelf on my assembly/outfeed table with a drawer for the cutters and attachments underneith. To use it I just lift it up, hook up the power and Bosch 35mm hose, and if it has the right bit, set the depth and height to what I need and start cutting mortises.
I don't think the two are comparable in price unless you are looking at a really nice floor standing hollow chisel mortiser. If so, it would work better than my benchtop since it should have a functional clamp to hold the work piece. You need a lot of clamp to resist the force of extracting the bit on the first cut. But that would amplify the space requirement difference. My shop is little so that is important to me.
I have not purchased any of the loose tenons yet. I bought my XL used and the seller included a bunch of 12mm tenons he had left over. I've used up all but 3 of those but I've mostly used tenons I made. Sometimes it was because I wanted a wider tenon. The 12mm tenon is just less than an inch wide. If you want a 2 inch tenon you can use two but you really need some space between them. Or you can plunge three times and make your own 2 inch tenon. I made about 100 100mm by 12mm tenons yesterday in an hour or two. Out of scrap. The purchased ones are handy for sure but you can make tenons and still save time versus cutting mortises with a hollow chisel mortiser and cutting and trimming tenons. The time required to make them is mostly setup so it pays to crank a bunch out when you are making them.
You also do not need a Festool vacumn. My Rigid and Bosch 35mm hose work fine. I think the domino is definitely a nicer way to go but quite pricey. A plunge router will make every bit as nice a mortise but takes more setup time. I cranked out three dozen mortises yesterday in an hour or so (each 2 inches deep, about an inch wide, and 12mm thick). You'd need a better hollow chisel tool than I have to do it in twice the time.