I figure, in order for me to beat a lower handicap player in match play, I need to limit my bad scores to come from a few blown up holes. That's easier said than done for a 21 handicapper. In fact, it only happens one out of about every 15 rounds. With 80% handicap tournament, I don't think I have any chance. At 100% giveaway, I think I have a decent chance to put up a fight.
Until relatively recently in the U.K. it was 3/4 of the handicap difference in singles matchplay. Initially, I, like a lot of others I know thought that going to 100% of the difference was going to be a big disadvantage for lower handicaps but after a bit of reflection and actually thinking about what's happened in genuine matches, it's pretty obvious that (sand baggers excepted and they soon get a reputation), giving 100% of the difference isn't that bad and the evidence actually still suggests that the low player has a slightly better chance than the high handicapper.
At the end of the day, if handicaps are an accurate reflection of the two players, giving 100% difference should be the obvious thing to do in my mind.