The fees which are applied by the respective exchanges should be considered.
When Purchasing LSE Stocks:
Stamp Duty Reserve Tax is charged at 0.5% on share purchases made for stocks listed on the London Stock Exchange. There is no Stamp Duty charge applied to gilts, bonds or ETFs.
PTM LEVY is charged in both cases, on purchase and sell, and it is £1 GBP per trade for orders over £10,000 GBP.
When Selling NYSE Stocks:
The Transaction Fee (Securities and Exchange Commission) is $0.0000207 of the value of the sale order.
The FINRA fee is charged on all covered stock and ETF sales at $0.000119 x quantity sold. There is a minimum charge of $0.01.
French Financial Transaction Tax
The French Financial Transaction Tax (FFT) is 0.3% and it is applied on the purchase of shares of companies located in France with a market cap of over 1 billion.