The following is an excerpt of a letter I wrote to a friend comparing the various Ticket to Ride variants. The official ones, anyway. I thought other people would find it useful.
Ok, here is the rundown. The dice add on, as I said, makes for a different, faster, but still enjoyable game. We like it a lot, but it does feel different from regular TTR.
Both the Nordic Countries and the Switzerland alternative are loads of fun, especially for small groups. They are both designed for only 2 or 3 players. Both incorporate rules for tunnels, and Nordic Countries has rules for Ferries. Very simple rule changes, but fun. Tunnels are specially marked train routes that may require extra cards to build them. It is random (you draw three extra cards every time you build a tunnel; if any match the color you are building, it means you need an extra card). The effect on play is that it is a little risky to build a tunnel route, unless you have collected a few extra cards of that color. We find it to be a nice rule addition. Ferries are routes that require either one or two of your cards to be locomotives. Also a fun addition. The maps themselves also have differences.
In Nordic Countries, the map has lots of short routes in the southwest, and lots of long routes in the north east. It means that depending on the tickets you select, your strategy will be different. In Switzerland, almost all of the tickets are easy, and short, and you tend to complete a LOT of tickets. Scores can run high in Switzerland. Both are lots of fun and we (Anita, my wife, and Heidi, our daughter) like them. Nordic Countries also has a Christmas-y feel to he artwork, so we often pull it out to play over Christmas break.
There is a Europe version, that is great for family play. He reason is that it allows you to build a Station if you like, on a city. It has the effect of allowing you to use a route that was claimed by another player, so being cut off is not as disastrous as in the other versions of the game. It really is only important for larger games, or games where one or more of the players are somewhat aggressive. The tickets for Europe are much more evenly spread out than the base game. Europe also incorporates tunnels and ferries.
There is a Legendary Asia version, that features a map stretching from the Ukraine to Japan, and from Siberia to India. It is a lovely map, and the tickets are the most spread out and even of all the variants. It features Ferries, and Mountain Passes. The latter require you to discard a train piece every time you build one. Those discarded pieces are worth 2 points each at the end of each turn, and they have the effect on the game of making the many short routes in the higher population areas of the map as being worth a decent amount more than the regular 2 or 4 points they would be in other versions. It is a very fun version and has a great feel to it, but less player interaction (like racing to complete a route) because of how evenly placed the tickets are.
There is a Team Asia version (the map focuses on China) that allows you to play as teams, possibly including a Sixth player. You can also play without teams, but the team rules look interesting. Each player has their own train cards, plus train cards that belong to the team. Team mates are not allowed to share info about what they plan to do, and can't show each other their non team cards. Looks interesting, but we haven't played the team version.
There is an India version that just is a different board, but one that is a lot of fun to play. It gives bonus points for completing tickets using two or more different paths. Very interesting feel, and a bit more competitive than other versions.
There is a Germany version called Märklin. Märklin is a German manufacturer of model trains, and they sponsored this one. Every train card has a picture of a different model train car on it of the right color. The map has Passenger markers on it at the beginning of the game, and a player may choose to collect all the markers on a train route instead of a regular play. Knowing when and if to do that adds another level of decision making to the game. I love this version, but Anita and Heidi have said it is the hardest to play, and quite competitive. I love the cards because I love railroading history, so maybe that clouds my judgement!
There is a Heart of Africa version, that has special cards allowing you to multiply your points for jungle, mountain, or desert train routes. I have not played it, but it looks beautiful (the map and the cards).
These are the official map board variants. Switzerland and India come packaged together. Legendary Asia and Team Asia come packaged together. Africa comes alone in a box. Europe and Märklin and Nordic Countries all come packaged alone, and they each include basic pieces (plastic trains and train cards). The others only have rules and ticket cards, so require a basic set to play.
Other than the variant map boards, there are four other add ons. First, already mentioned, are the Dice, which work with any variant, but building the special 9-car ferry in Nordic Countries would be very hard using the dice system.
Another (Excellent) add on is the 1910 box. It has very nice full sized train and ticket cards for the North America game (I really don't like the little cards, they are fiddly and hard to shuffle). It also includes a number of variant ticket cards hat each give the basic game a very different feel. For a small add on it really improves the game experience (better cards) and gives lots of different game play alternatives.
Europe has a similar boxed add on called 1912. I also adds extra tickets for Europe (the Europe base game comes with larger cards, they learned their lesson after the first set), and another variant. This is the Warehouse, which is a way to collect extra cards that come in handy.
There is also the Alvin and Dexter add on. Alvin the alien and Dexter the dinosaur are plastic pieces that move around and block cities from being developed. Very cute, but it was not a favorite at our house.
Finally there is the Halloween add on. It is a full set of plastic trains in gray, witH plastic pumpkins in them. Very cute, and a nice add on set of pieces, but no real changes to he rules.