I do not personally believe there is that much learning curve between a 600 watt and a 1000 watt. Lower wattage lights require more skill if anything. They do not penetrate that well so more advanced training techniques like scrogging are needed to truly maximize yield. 1000watt lights offer greater penetration, you can top your plants once to create some extra heads and from top to bottom your buds will be well developed, where a 600 watt will only give you a top canopy. This lets you use a shorter veg time since you don't have to do excessive training, and if you do desire to do extra training, it'll pay off twice as much.