So, it appears that there is abrogation here, from initially delegating to the Prophet to finally fixing the percentage of distributed shares of booty. That is if we concede that the gain referred to in both verses is identical, otherwise there would not be a conflict.
That is the understanding of Qataada, writes Dr. Mustafa Zayd in his book النسخ في القرآن الكريم, volume 2, pages 261-263 (items 1146-1151), and it is the basis for this claim. Dr. Zayd rejects it, however, by showing scholars opinions that
الفيء, referred to in 59:7 means income or revenue, while
الغنيمة, mentioned in 8:41 means booty. The former is obtained without fighting, while the latter is obtained only after a battle. At-Tabari mentions this interpretation, favors it and backs it up by a narration attributed to Mu`ammar.
Dr. Zayd also states that Ibn Al`Arabi's and An-Nahhaas opined similarly and stated that there is no abrogation her. And he concurs. Dr. M. Ibrahim Faaris also concurs in the footnotes of page 178 of his book صفوة الراسخ في علم المنسوخ والناسخ and attributes this analysis to Makki and implies that Abu-Abdillah Shu`la agrees as well.