My experience is that the 'separate but equal' dual engineering track is largely a myth and that if you want advancement, the manager track is a much more viable track. Even with some of the recent flattening, there are still far more higher level roles for management than ICs. They are also given far more visibility and access inside the company which is extremely valuable in a large org. It also seems a good choice if you're not very good - I've seen bad managers hang around far longer than bad engineers.