CraftBukkit and Spigot are essentially the same thing - changing between them will not change anything in your plugins (assuming none of your plugins are heavily outdated, as some particularly old plugins won't work with Spigot but its a very very small chance).
Both are updated by the Spigot team themselves now - Spigot is simply CraftBukkit with additional performance patches and tweaks applied to it but it will run the same plugins exactly the same. Spigot is suggested to be used in general over CraftBukkit.