Lumens are not how we see light. How we see light is entirely subjective: 1 lumen can easily appear as bright as 10 lumens once one's eyes have adjusted. Lumens is the [objective] measurement of how much visible spectrum electromagnetic radiation a source emits. The photosynthetic spectrum happens to fall almost entirely within the visible spectrum (with the exception being a small amount of ultraviolet and a negligible amount of infra-red). This means that lumens is a fairly accurate measurement of light-available-for-photosynthesis. Of course spectrum within the visible spectrum plays in a great deal, but 1000w and 600w bulbs have practically identical color spectrums. So 100,000 lumens put off by 600w bulbs is IDENTICAL to 100,000 lumens put off by 1000w bulbs; it will penetrate the SAME if concentrated on the same size area (something like raptor dual bulb reflectors would be good for that). The only difference is that 1000w bulbs are less efficient at producing the same quality light, concentrate heat and light less evenly, and allow less customization per wattage as far as different bulbs and spectrum go.
edit: 1000w bulbs also produce more heat per watt than 600w bulbs, due to the decreased luminous efficiency.