Originally Posted by
AlwaysAisle
Fares on Hikari and Kodama are same, but likely you will have better chance to get a reserve seat on Kodama. However, also note that Hikari has snacks and drinks sales by wagon onboard, where Kodama does not have any snacks or drinks sales onboard.
Though this is true, I would always recommend station bento / "駅弁" over onboard sales for a delicious train experience.
These are typically available inside the shinkansen gates.