Re: TTR Märklin and TTR Märklin Collector's Edition
I'm not sure there is one. Both my copies are labelled "Collector's Edition" so I cannot compare. But everything looks pretty much standard for the game given that it uses pictures of Märklin model trains throughout. Every single train card is unique, but I think that was true for all editions.
I agree with this. I have never heard of any differences, or, by the way, any different editions of TtR Märklin at all.
They might refer to the facts that
1) Ticket to Ride: Märklin is a somewhat more complicated game than original and Europe versions, thus maybe aimed for a smaller gaming community than them.
2) Märklin in itself is a well-known model railway manifacturer, so people more interested in trains and/or model railways than in games, are probably still interested in playing a game closely knit to Märklin. Or just buying it to get the train cards?