I'd take a lump sum. With my health, I don't expect that I'd have 25 years to collect incrementally. In Canada, we don't pay tax on lottery winnings, so a lump sum on 50m here would be around 40m. But to keep thing consistent, here is what I'd do with 20m:
1) 4 million to my family
2) Up to 1 million for transition expenses
3) Up to 1 million for a penthouse in one of: Toronto, Montreal, Berlin, Stockholm, or Amsterdam
4) Up to 1.5 million for vacation homes in three of: Paris, Madrid, Halifax, Tokyo, Manhattan, San Francisco
5) 8 million invested for living expenses (never eating into the principal)
6) 4 million for travel
7) 500k for misc expenses
When I die, my properties will be sold off and, with my untouched 8 million, the money will be used to set up a foundation for the arts.