I checked that way, tickets are expensive by at least 200 bucks. I tried MCO to KIX/ITM and while coming back from NRT to MCO.
Considering the fact that the price of the Shinkansen from Tokyo - Kyoto - Tokyo comes out to $200-300USD give or take already, you're breaking even abouts, while saving yourself some time and effort. So going into KIX and flying out of NRT might work out better.
The speed between the Nozomi and Hikairi isn't great, the Nozomi makes just fewer stops so its slightly faster in time not speed.