Now, if we don't refer to the fact this is a lottery and to the win chances, if the inflation rate doesn't go nuts, the monthly payments seem the better option over 30 days. They would pay 7.2m Euro over the period, and inflation erodes the 20k payments over time, not from the start. Frankly, I'm not versed enough in this area to calculate which of the two options would be better, let's say, if you have an average yearly inflation of 3%.