I usually say "harder styles of techno" because most people don't know what the hell Hardtekk, gabber, hardcore, Speedcore and Extratone are. Especially Extratone gets quite a lot of undeserved hate. Most people shit on it without even knowing what it is and that it isn't monotone beeping. Melodic Extratone is absolutely great and it uses techniques that you can't do with other genres.
Hardtekk is a genre quite popular in Germany. Its know for having not much melodies, being repetitive and using a lot of distortion so that everything sounds a bit cheap. It is also quite popular in combination with German rap.
Speedcore is techno with 400+ bpm and Extratone is everything above 3600 BPM. This is The Rate at which the beats turn into a single tone and you can't hear the single beats.
Hardcore is the evolution of Gabber with harder kicks and a usually darker theme. Nowadays hardcore is heavily influenced by Uptempo. This is why I prefer the old school hardcore over the newer stuff (Uptempo is cool, but I want to listen to hardcore but Uptempo light).
Another genre I like to listen to is terrorcore which is insanely brutal underground hardcore.