The Hyksos hypothesis requires no special pleading, but the Akhenaton one does. The evolution of tribal legends, over centuries, is completely normal and expected. The Hyksos hypothesis is considered the most plausible because it best accords with the evidence/ It provides the basic outline of a semitic, Canaanite people migrating into Egypt, gaining power, coming into conflict and leaving.
The Akhnaten hypothesis has nothing to really support it, and (in my opinion) the biggest problem with it is that it ignores the fact that the Israelites were not originally montheistic. They originally used the Canaanite pantheon, then became henotheistic (somewhere aroind the 8th Century BCE. They didn’t become truly montheistic until after the Babylonian exile, so there is no continuous line of monotheistic belief or practice from Akhnaten into Canaan. The Israelites didn’t get their monotheism from Egypt, but from Zoroastrianism 800 years later. There is a about a 200 year gap between Akhnaten and the emergence of the Israelites, with no pre-Israelite Canaanite practices during that time, and not even any Israelite monotheism for another 600 years after that. There is simply no connection between Akhnaten and Jewish monotheism, and without that commonality, there is nothing at all to connect Akhnaten to Israel.