Alex,
It actually wasn't my idea. I'm really not that smart. And maybe I re-stated it wrong but I was told by Festool that there are differences in the balancing system between the two and if interchanged you would not get optimal minimal vibration. Maybe it's not the exact part, rather how it is designed, I'm not sure. And even if they took the time to more fully explain it I may not totally understand it. They just said the counterbalancing is different for each sander. It was probqably my assumption that the actual weight was different.
That being said: I suppose anyone is welcome to change their pad anyway. However I thought I would relay the info from Festool as to why they aren't interchangeable. Posibly some people wouldn't want to make the change having this knowledge.
No offense to you at all but if Festool tells me they are different in how they are balanced and shouldn't be interchanged, and you tell me they are the same...again no offense meant at all to you, but I think I'd rather rely on information directly from festool. Others on here may too. I suppose there are some who would deduce that Festool just told me that so they could sell two sanders instead of one, but I am not a conspiracy theorist, so I take them at there word. And I suppose the person at Festool could have been mistaken but again I'd rather err on the safe side.
For me personally, at the moment it is a moot point, since I don't have either sander, I will wait until the new one comes out. Even if I had both sanders I wouldn't try to interchange them. I'd rather have both sanders since they aren't that expensive and I'd rather not have to deal with the hassle of making the changes back and forth. (I have two band saws in my shop so I won't have to change blades as often)
Not to mention it may void the warranty even if I didn't screw something up taking it apart.
Just my take on the subject.