If your unit is $100 let's say, I think most people do it where they would risk the $100 to win $200 rather than risk $50 to win $100.
Even when you call a sportsbook to make a bet and it's at plus odds, it seems they expect you to say "Risking....$__" and if you take a favorite at minus odds, they expect you to say "To win...$__".
It all depends on your bankroll, money management, etc. Some people might easily like it more doing it the other way. They get more satisfaction out of saying "Well, I lost but it was worth taking a shot for $50 to win the $100...at least I only lost $50...etc, etc". It all comes down to how conservative you want to be.