I strongly believe you should form a core portfolio with a minimal number of ETFs which will cover the broad investible market as close as possible, at low cost. VWRL (IE based) and VT (US based) are one stop shops for the beginner investor, but can be improved upon.
My short list for IE-based ETFs:
XDWL + IUSN (or WOSC) + EIMI
covers 100% of the MSCI ACWI IMI universe with a market cap weighted average TER of 0.2%
My short list for US-based ETFs:
Vanguard:
VTI + VEA + VWO
for weighted avg. TER of 0.06%
or
Ishares:
ITOT + IDVE + IEMG
for weighted avg. TER of 0.05%
Keep in mind that whichever way you go, the transaction costs of trading via a Swiss broker will likely be higher than any differences in TER.
There is also nothing wrong in looking for opportunities in countries/sectors or even single stocks which trade at a discount due to recent events. You have to know what you are doing, and why, or simply accept the fact that this is nothing but a bet. For example, buying VW at the depth of the diesel-scandal would return quite a nice profit (+70% as of today). As a contrary example, if you bought a Greece ETF at the depth of the finansial crisis in 2008, you’d lose an additional 80% as of today.
Mainly cost and tax on dividents. See this excellent post buy nugget: