That is about as concise a way of describing these strategies as I can imagine - 100% correct, although you can combine the 2 for an even more effective approach (getting the timing right on the switch-over is crucial). Wyndstar's Altarian AAR (linked above in Mascrinthus' post) describes this style perfectly.

For a zero year win at the higher levels, the key is in eliminating the AI before they have a chance to leverage their huge bonuses into a position of strength, that they will be hard to dislodge from. Don't think of a zero-year game as one that needs to finish within 48 turns, aim for finishing in less than 20 (13 turns is the ideal number for MV games).

Last few games I've been going all labs for about the first year. After I have the techs I was aiming for I switch to all factories for a year or two for build up(infrastructure), then it's all econ from there on out .

Used to use all factories from the get go, but it was really difficult to get the techs I needed by the times I needed them. At that time I would have to compensate by outcolonizing the AI enough to have a large planet base to draw focused research from. It's difficult though to outcolonize them on obscene and I still haven't been able to do it on suicidal, thus the different current strat .