The gemara says that the penalty of paying keifel and daled v'hei, is only for a ganev who hides his actions from people, not for a gazlan who steals in public. Why? Because a ganev expresses a special chutzpah by showing that he is afraid of people but not G-d - כביכול עשה עין של מטה כאילו אינה רואה ואוזן של מטה כאילו אנה שומעת. But a gazlan at least equates the kavod of Hashem with the kavod of people, so there is less chutzpah in his actions. Many years ago (14 Teves 5761), I had a question based on the halacha found in Hilchos Shechita (siman 2) - One who violates Shabbos in public is considered a mumar for the entire torah tantamount to one who worships avoda zara, and his shechita is passul just at the shechita of a goy. But, one who violates shabbos in private, although he is not trusted, so long as there are mashgichim who determine that he shechted properly, his shechita is kasher. Based on the gemara's logic by ganav and gazlan, we should consider a mechalel shabbos in private to be worse than a mechalel shabbos in public?
R' Moshe (Igros O.C. 1:33) raises this question and based on it is mechadesh an important yesod. It is not clear why a mechalel shabbos in public is so severe, but R' Moshe suggests that one who violates shabbos in public is not just a מומר לתאבון, but the fact that he is doing it in public indicates that he is a מומר להכעיס. Although the concept of the gemara is true, that one who steals in private and hides from G-d is worse, that is when both the act in private and the act in public are for the sake of filling his desires - לתאבון. But when one violates shabbos in public he enters a new realm of being a מחלל שבת להכעיס, which is certainly worse than merely being motivated by desires. Even if deep down he is only doing it to satisfy his desires, דברים שבלב אינם דברים and the act is an act of להכעיס. Based on this he suggests that this only applies at a time when people understand the severity of shabbos so that when one violates shabbos publicly, it is an indication that he has a complete disregard for the shabbos, but nowadays where people no longer take shabbos seriously, and their desires would bring them to chilul shabbos in public just as fast as it would bring them to chilul shabbos in private, even one who is mechalel shabbos in public will not have the status of a goy (therefore his shechita is kasher and he can be counted for a minyan).
I had an alternate approach to answer this question. Stealing is an aveira בין אדם לחבירו that every society recognizes as wrong and destructive. It is part of human nature to consider theft to be bad, and is inherent in human nature to try and hide these actions from others. When one hides these actions from people because he is worried that people will think less of him, or may catch him to punish him, he is outwardly displaying a fear for people that exceeds his fear of G-d. Since it is part of human nature to hide acts of theft, we assume his intention is to hide it from other people. However, Shabbos is בין אדם למקום, and therefore the violation of shabbos is not considered bad by human nature. When one hides his chilul shabbos from others, we assume that it is not because he is afraid of people, because people don't view chilul shabbos as inherently bad. So why would he hide his actions from people? We assume his attempt to hide his chilul shabbos is out of respect for Hashem, rather than trying to hide from Hashem. But when he is mechalel shabbos in public, we consider it to be a lack of respect, violating shabbos in the open showing no regard for it at all.