Regarding the plunge function, watch these videos for a good comparison of the plunge functions:
Mafell KSS:
Festool HKC:
On differences for the MT55cc vs TS55R:
The Bosch/Mafell tracks are superior to the Festool tracks if you need to join two or more tracks together. They self align using the connector pieces. The MT55cc will ride on Festool rails as well but tilt for cuts will be off.
On the MT55cc's plunge depth scale, the indicator rotates to adjust for on versus off track cutting depth.
The MT55cc has a fully sealed side. Mafell did some heavy overengineering for the lock that opens the side up and added an airflow pathway inside the side. Not only that, the opening for the arbor to go into the housing is smaller than the TS55R. The TS55R is the plain old hole on the side, plunge the saw down and it locks into position for you to use the allen key to fiddle the flange and bolt off.
The airflow pathway design is impressive to me, there's a small bit of rubber or sealing material that lines the two halves of the casing but inside partition is left intentionally open as a slit with both sides not fully extending so the sawblade teeth can help accelerate airflow. You can feel the air blow out of the exhaust port with force on the MT55cc. The TS55 doesn't play nice if you use it without dust collection and can get jammed full of chips. The TS55R I don't think has the problem that the TS55 has.
There is a built in clear front chip catcher that slides down to maximize dust collection on the MT55cc, which is present in the TS55R but not the TS55.
The MT55cc locks the tilt with one knob using a linkage that simultaneously locks the rear as well. The MT55cc also has a -1 and 48 cuts but has a positive zero and 45 degree stop. Festool did something with the early version of the TS55R which had some iffiness on the zero stop which couldn't be retrofitted to earlier serial number TS55Rs. The TS55 didn't have the zero stop problem.
Speaking of tilt, there is a sliding indicator on the front of the MT55cc if you tilt it and use it off the track that shows the cutting position of the blade.
The paint/texture used by Mafell on the MT55cc's metal components is something I have only seen on very expensive camera lenses from the 90s (And later): A crinkled surface with a hard paint on it.
The MT55cc also has an optional accessory for knowing the exact start and end of a plunge slit is that attaches to the side and slides to several settings.
The MT55cc also has two options for a fence, a simple straight parallel fence and one that is rolled over. The latter fits on the KSS400, KSS60cc and MF26.
The Festool TS55R uses a plain bearing for the thrust bearing. The Mafell MT55, Festool TS55(Non R), Dewalt tracksaw and Makita tracksaw all have ball bearings from the parts diagrams.
Festool's body plastic doesn't feel particularly sturdy (MT55cc vs TS55r and P1cc vs Carvex P420). Mafell seems to machine down a lot of precision surfaces whereas Festool leaves the casting as is. You can ask the guys on the official Festool forum about the bottom of the Kapex where the casting is rough. You can also compare the replacable foot system on the Carvex versus the machined surfaces on the P1cc. Everything about the MT55cc base and housing seems to as perfectly finished as you can get on a portable power tool to me. I mean it, I cannot find any indications that the parts were rough castings that were lightly touched up. Between the crinkle textured paint and machined down surfaces the MT55cc sits alongside with the fit and finish I'd see on some high end photography gear, precision measuring insturments and 5 to 6 figure metal working machinery.
The MT55cc has the scoring cut feature which also is tied into some kind of unique plunging geometry that allows it to offset the blade to the side slightly.
The MT55cc has no riving knife as it uses an electronic anti kickback system which cuts power to the motor when it thinks a kickback condition has occured. I have not experienced the system working but I've been able to use super thin sawblades due to the lack of riving knife.
The MT55cc spins faster at max RPMs.
The MT55cc also has more power than the Festool TS55R, see these videos from JAlvis:
The biggest flaw I can find with the MT55cc is I kind of wished there was some kind of front handle or a handle/knob that came off the plate like the KSS saws. Most of the other tracksaws have the front handle attached to the motor. Maybe I can make a few other nitpicking points about the MT55cc.
That's all I can think of right now off the top of my head. I will post a video of the extremely (In a good sense) overengineered mechanism that opens the side of the MT55cc later. That alone was impressive to me when I noticed what Mafell did for it.
Edit: Video of the cover lock
mafell-users-forum.freeforums.net/thread/765/mt55cc-blade-cover-detail-video