Sixt try very hard to be on the top position for rental car companies. I am usually happy with them. The staff is certainly better trained and more polite as by other companies. But... the platinum card only gives a small discount on the price and NEVER an upgrade as they wrongly pretend. You are not entitled any free weekend as for europcar. My latest rental car has some serious motor issues. To be fair, it never happened in the past. To conclude, Sixt and europcar are both serious companies, Sixt is more courteous.