Do you have sufficient cooling? HID's will put off some heat.
If you can control the temp, 1000w HID will give you excellent results. I've heard of people using the LEDs for just vegetation but I'm not sure about going into flowering with them.
This appears to be an example of MH vs LED
http://www.ledgrowlights.com/led_grow_lights_v_hid_lights__copy(1).htm,
This is what I was able to gather from a simple search:
Wattage Approximate lumen output Garden area covered Area covered with grow light
250 watt 28,500 3' x 3'/ 9 ft2 4' x 4'/ 16 ft2
400 watt 50,000 4' x 4'/ 16 ft2 6' x 6'/ 36 ft2
430 watt 53,000 4' x 4'/ 16 ft2 6' x 6'/ 36 ft2
600 watt 90,000 6' x 6'/ 36 ft2 9' x 9'/ 81 ft2
1000 watt 140,000 8' x 8'/ 64 ft2 12' x 12'/ 144 ft2
****This is just a rule of thumb. We recommend doubling the wattage for maximum results.****
White/blue = propagation (seeds/clones)
Blue = vegetative (growth)
Red = Flowering (bloom)
Our Tri-Band LED grow lights are engineered to out perform all of the traditional metal halide and high pressure sodium style lights, including: 100W Metal Halid, 400W MH, 600W MH 1000W MH, 100W High Pressure Sodium, 400W HPS, 600W HPS and 1000W HPS
Red Light
Red Light much like HPS is in the vicinity of the first peak of a plants light absorption spectrum (660nm) and it contributes to the plant photosynthesis. Red light, when combined with blue and orange light, encourages flowering. It can also be used in higher doses to stimulate flowering, seeding and fruiting.
Blue Light
Blue light much like MH is responsible primarily for vegetative growth (leaf). It is known that chlorophyll has the second distinct absorption peak in the vicinity of blue light wavelengths (450nm). The blue light is also indispensable to the morphologically healthy growth plant. There is also more sunlight energy in the blue-green wavelengths
This may be an incorrect analogy but if you're into cars, the way I would compare the two is the HIDs being a muscle car and the LEDs being little 4 bangers filled with NOS and supercharged etc etc.
Can anyone weigh in on the LEDs?