Some funds are available on SIX and LSE. Are there any particular pros/cons of either (both USD currency):
Go where the volume is higher (lower spreads).
Which broker do you use ?
To avoid FX fees, it’s also better to invest directly in CHF
I use IBKR. To avoid FX fees I would use USD as my funds are already in USD (the underlying fund is also USD so any CHF purchases would be converted behind the scene).
In this case, if you buy in USD, all exchanges where this security is traded in USD form one liquidity pool. If you use smart routing, the order will be just sent to a trading venue with the best conditions.
The trading volume is relevant for margin loans.