The biggest difference is the most obvious one, the Gen 3 has a shorter cable at 18 feet. If you need the longer cable then the Gen 2 is for you.
If you have a spare 100 amps of capacity in your breaker box / service, AND specifically plan to buy a car with the Twin charger / hi-power charger, then you might want to get a Gen 2. If you go above a 60 amp circuit, then you should install a lockable disconnect just ahead of your Gen 2 station. I personally find this a comforting addition but many don't like the expense and size of these things.
As someone with a fresh setup, you can go with the Gen 3, and a 60 amp circuit and be quite happy. The Gen 3 is easier to install and will be supported by Tesla for a much longer period of time, so replacements will be easier for quite a while on the Gen 3. The Gen 3 should also be able to load share if you add more of them down the road, but not in the same way as the Gen 2. Each Gen 3 get's it's own circuit, then you tell the software what they have available to share. This is simpler to implement than the junction box implementation and communication wire required by the Gen 2. Plus when you go to expand the Gen 2 will probably be unavailable, or at least very expensive.
These things don't break that often, normally they are victims of their installation, or abuse of their owners. But if a Gen 2 fails at some point in the future you are almost certainly going to end up with something else as a replacement.
My house has four high power (80A capable) J1772 stations using off the shelf hardware, if any of them break I can replace the parts and get them running again. I am also not locked into Tesla, which is good, because I own two other non Tesla EV's. Owning a Tesla unit locks you into driving a Tesla, to some small degree. You can obviously change it, but that is an added expense and scheduling challenge if you drive your Tesla into a dealer and drive home in something else. J1772 requires an adapter and with that you lose the simple push button charging door open process. There are ways around that.
Hope that helps!