A.G.:
There are several ways theandicap system is built to benefit the lower handicapper.
1) ESC- reduces abnormally high scores. Since higher handicappers' scores are more volitile, more of their scores are adjusted downwards. I am a low handicapper. I adjusted exactly one hole score in all of 2006. Many higher handicappers adjust one or more hole scores downward every round. Thus their posted scores are often two or three or more strokes lower than their actual scores.
2) Averaging the ten lowest of the last twenty differentials. This is really the same as #1- scores for higher handicappers are more volitile, and the ten highest diferentials are eliminated.
3) Then average of the ten lowest differentials is multiplied by .95. This is called the "bonus for excellence." For example, if player A's average differential is 0, 0x .95=0. If player B's avg. differential is 20, 20 x .95 = 19. I.e., the "bonus" cost the higher handicapper one stroke for his match against A.
My 55% - 45% example is an approximation. the exact percentage would depend on how far apart the handicaps were. Two scratch players should split 50-50, and the percentages would get wider as the handicap differences get larger.
You may agree with Archie and that's OK, but I'll go with the guys who set up the system.
The problem is that the system is just that, a system, and if it is not followed very close to exactly, inequities result. So the 80% recommendation fits the system. If you are playing with people who are not true to the system, your perception of what is "right" may be different than the recommendation.
Finally, handicaps are calculated individually. They are equally effective in individual stroke or match play, where they are used at 100% (some local tournament committees may choose to go with a percentage, but it is unlikely they have a good reason to to so. They are helping the better player, but if the better player also has a suspect handicap, what's the point?)
The recommendations for four ball take into account that there are two players but only one ball counts. Thus the effect of volitility, the concept that the higher handicappers' scores will vascillate more than the lower handicappers', is greatly enhanced. It makes sense, then, to regulate that volitility somewhat, to the advantage of the better players.
Hope this helps.