[angersock]

Neither, because you'll either get burned out or full of trivia that is not useful.

Instead, pick some practical projects, and work on those. Maybe a music player, or a game. Games are good because they bring you through the whole spectrum of high-level abstraction (how should I build this system?) to the low-level drudgery (oh god why is this buffer getting corrupted how do I fix this aaaagh).