Advanced hybrids have more plans than implemented stuff, at this point, but there are a few things:
1) They can mature to the highest tier, allowing them to use the highest mark level of their modules and to coordinate MarkV drones, and get the highest tier of builder modules, etc.
2) One of the highest tier builder modules lets them actually build more Hybrid Hive Spawners, which means they can really increase their own spawn rate and population cap and explode out of control (less so with the population limiter logic put in more recently, to avoid swarms of 1000s of hives, etc). Also allows them to rebuild if you almost wipe them out.
