They are all great saws and I do not think you can go wrong with any choice. I have them all and use them and it comes down to what is most important to you. First off, I prefer Festool rails to Mafell because of the green anti-glide strips on the rails and they are grippier on the bottom. With the TSO connectors, joining rails is not longer an issue.
For Mafell:
Pros:
In terms of power, blade change and dust collection - Mafell wins hands down. It also works on Festool rails and Bosch/Mafell rails. Has the ability to score cut, which is nice for Melamine and other sheet goods. Standard blade is 162mm, so cuts slightly deeper than Festool. Takes both thin kerf 1.8mm blade and regular 2.2mm kerf blades. If using Mafell guide rails, you can clamp right next to the cut edge - which is nice for thin strips or working with narrower stock. Aligning rails is super easy too.
Cons (which may or may not be a con to each user):
No off cut anti-splinter capability, no riving knife, 45 degree bevel does not line up to FT or Mafell splinter guard; no Plug-it cable. Rail square is not readily available in North America -- some providers in Europe offer them, but not cheap/easy to import them to the US.
Even though only one dealer in North America, Timberwolf Tools is a great company to deal with and no issues whatsoever with anything I have bought. I even had a warranty issue and they just sent me a brand new tool and I shipped the broken one back...no questions and at their cost each way.
Festool:
Pros:
Lots of dealers and after market accessories available - TSO makes great rail squares and other accessories. More readily available to try and use. I find it works great and after sales support is great. Anti-splinter on off cut; riving knife.
Cons:
Does not have as much power as Mafell - which may or may not be an issue - only takes 2.2mm blades with riving knife, but FT options cover all the bases and are high quality. Not as good of DC as Mafell, blade changes not as quick or easy as Mafell, no scoring.
I would also consider the cordless variants of both saws - the TSC is very good and overcomes the power/torque issues the corded version has. I really like mine and 2 sets of batteries can keep you cutting all day long. You can take it anywhere too, which is nice. I do not have the Mafell version, but I understand it is a great saw too and folks enjoy using it.
Hope this helps.