I haven't tried very many different MH reflectors, so not sure my opinion is worth much. I built two Lumenarc 3 reflectors using 'solatube' reflective' aluminum from the reno center. I basically gutted a very dated MH/VHO (even had a couple of MR16 LEDs) combo fixture to cobble together my own light rack made of square & angle aluminum stock from Princess Auto. The old fixture was a beast & had 'spider' reflectors for the 2 MH 250 watt moguls. The previous owner had somehow neglected to remove the protective blue plastic film from the inside of the fixture and it was essentially burnt into the aluminum reflective material. There's no way I could get the stuff off any longer, that's one of the main reasons I decided to gut it. The VHOs had internal reflectors inside the lamp and only one of the LEDs was working when I purchased the used system it was on.
In addition to fabricating the Lumenarcs, I used the two Workhorse 8 ballasts which powered the VHOs and converted them for use with 4 x 54 watt T5HO retro parts. I've since removed two to the T5HOs and only run two. Anyhow, the home built Lumenarcs work one heck of a lot better than the old spider reflectors, that's for sure.
Here's a photo from a while back, but the fixture is still much the same, other than some changes to the fan set up.
