Router fragmentation is no longer allowed, that can be a cause (this is covered by your edit). One less checksum. On the meta level, core routing tables are m

Router fragmentation is no longer allowed, that can be a cause (this is covered by your edit). One less checksum. On the meta level, core routing tables are much simpler but the use of CAM means that lookups are an O(1) operation, therefore any speed improvement would be due to the better scrutiny and route simplification that a smaller number of routes can afford. All this is offset with the v6 header being 40 bytes rather than v4's 20 bytes.