There is no simple answer as what is the best or cheapest will depend entirely on where and how much travel you do.

As the passes get cheaper per day the longer duration they are it can often be better to have one long one than several short.

Interrail Passes are best for periods of reasonably long travel, for time spent in one country or region or particularly around one city then there can be better options available locally. City/region travel especially as local tickets will cover metro/tram/bus and even boat where Interrail is mostly restricted to mainline rail.

Although only you can choose the best option, it is quite an easy calculation to determine your best choice.

You will be over here about 4.5 months and doing a lot of rail travel.

So for example you may choose 2 * 2 month continuous passes (2 * 903 AUD = 1806).

You could also go for 2 * 15 days in 2 months (2 * 611 AUD) which would work and leave enough to buy a third flexi pass if you needed a few more travel days.

and so on.

Don’t forget your Eurail pass is usable across Europe including Switzerland.

Also do not overlook that CH=Swiss is about, after NO, the very most expensive country in all or EUR-your cost you need to spend per day will be considerably higher as down yundah in OZzieland. Unless you have family or whatever other means to cut that cost.

IF you want so save on travel expense, it would most likely be smarter to spend that 1 month at the end and use a 3-MO pass before. But even local travel in Swiss is quite costly if you do not know how to, and all these mountain lines etc that all those from far away want to ride are not covered by that pass.