The AI Hydra 64HD is the fixture most reefers buy because it does almost everything well. It hits 200-350 PAR over a 24x24-inch area at 18-22 inches off the water, runs cool, controls cleanly through MyAI on phone or desktop, and has been on the market long enough that the firmware is stable. The spectrum is strong in royal blue (455 nm) and violet (405 nm) with a usable white channel for daytime viewing. Weakness: the optics are slightly broader than the Radion equivalent, so you get a softer pool of light rather than crisp peaks. Most SPS-dominant tanks do fine on Hydras; very deep tanks (24+ inches) sometimes need an upgrade.
The Radion G6 line, particularly the XR30, is the fixture coral-photo enthusiasts buy. Tight spot-style optics produce dramatic shimmer and the XR30 hits PAR numbers in the 400-500+ range at 18 inches off the water with the right channel mix. The Mobius app is more capable than MyAI for power-user scheduling. Weakness: the XR30 is overkill for tanks under 60 gallons and the upfront cost is significantly higher than equivalent Hydra coverage. Also runs hotter than AI fixtures and benefits from a small clip-on fan in tight canopy environments.
Reefi has cut into the AI/EcoTech market by offering similar or better PAR per dollar with a clean app and reliable hardware. The UNO MAX is a direct competitor to the Radion XR30 at roughly two-thirds the price. Spectrum is reef-tuned and proven on hundreds of SPS-dominant tanks documented on Reef2Reef. Weakness: ecosystem is smaller (no doser-light coordination the way EcoTech offers) and resale value is lower than the bigger names.
Orphek is the choice for tanks deeper than 30 inches or for hobbyists who want one-fixture-covers-everything for large displays. The Atlantik V4 and the newer Compact run higher wattage with broad-coverage optics designed for 36+ inch coverage zones. PAR at depth is unmatched in the consumer market. Weakness: highest upfront cost, app is functional but not as polished as Mobius, and the fixtures are large enough to dominate a tank canopy aesthetically.
Kessil A360X uses a different optical approach - dense matrix LEDs producing intense shimmer with a more "natural" look than panel LEDs. Often used for show tanks, soft-coral tanks, and frag tanks where aesthetic matters more than maximizing PAR per square inch. Spectrum is fixed-blend across two channels (color and intensity) rather than the multi-channel control of AI/EcoTech. Weakness: less control granularity, lower PAR per dollar than Reefi or AI for SPS-dominant systems.
For a standard 24-36 inch reef tank running mixed reef or SPS-dominant, the AI Hydra 64HD is the safe bet. For a high-end SPS display where photography and shimmer matter, step up to a Radion XR30 G6. For a budget-conscious buyer who wants Radion-level performance for less, Reefi UNO MAX. For a deep tank or 6-foot display, Orphek Atlantik V4. For a soft-coral or frag-tank aesthetic, Kessil A360X. Coverage rule of thumb: one fixture per 24-30 linear inches of tank length, mounted 8-12 inches above the water.