It does really matter. It's certainly better to have x% chance to win y, than x% change to win z, for z < y. Psychologically, if you assume you lose (and you're "kicking yourself") then avoid betting on popular sets, because it's better to miss a chance to win $100 000 (10 way split) that you would get by betting on a popular set, than to miss a chance to win $1 000 000 that you would get by betting on a unique set.