Spigotmc is better :Pcause the server cannot use spigotmc 1.7.9 because of the lag as the owner said so im suggesting to use Bukkit instead I'm pretty sure its not going to lag cause I tested both of them in a lan server and Bukkit was working fine
Spigotmc 1.7.9 is laggy, but if you used Bukkit 1.7.9 it wont lag and the skins will work fine