There's a lot of sellers offering the "old" Panther blade for a relatively small price. "Way to go, an original Festool blade on the cheap!" one thinks and is easily persuaded to buy one.
Don't.
I have one of the old Panther blades for my TS55, for use in my CMS setup. It rips quite a bit easier than the fine-tooth W48 blade, but the quality of the cut is nowhere near Festool standard.
Don't even think of using it with a guiderail as you'll ruin your splinterstrip.
The new Panther blade is said to be better, and at least shares the kerf-width with the other blades. The geometry is said to be different, so maybe the quality of the cut is way better - then again, it has even less teeth ( 12 vs 14 for the "old" Panther blade ) so I'm not so certain beforehand.
The universal blade OTOH rips hardwoods almost as easy, and delivers a nice, clean cut - if you're careful and don't burn or burnish the cut, it's glue-ready right of the saw.
Just my two Eurocents...
Regards,
Job