If the specs of the fixture, namely lamp quantity, length, and whether or not it has individual reflectors match that of another fixture, the light output should be somewhat similar.
Is it possible they aren't cutting corners? Sure... but I doubt it. It's all a matter of where they are getting their components from and the quality of them. That's where we come full circle to what I was saying about electronic ballasts. While it sounds like that's a positive selling point, it may not be, because there are more ways to cut corners with them.
More importantly, there are other intangibles that are different from what actually comes in the box. For one thing, there is considerable R&D that manufacturers put into their systems to give them the best possible light output for every watt of energy you burn to them them. Other manufacturers may not be so concerned about that. Because they are unethical? No, because they know that their clientele is more interested in low cost than better performance.
Then there is service and support. I'll give you an example. I am an IT guy. I only buy HP Proliant servers. There are vendors that will sell me a server with identical specs for less than half the price. Why do I buy HP? Because I know that HP has tested a million times over their machines before they sell them, and if ANY part breaks on the server, I will have a new part on my loading dock the next morning, no questions asked, no shipping charges, no nothing. When I have users that require my systems to be online 24x7, that extra bit of money up front pays back 10 times over when a failure occurs.
What I'm saying is that when you look at these odyssea fixtures, you need to look at the reputation of the vendor selling them, the warranty support, etc. So what if they say they have a 1 year warranty? A pantload of good that does you when you have to ship your fixture into them to get it fixed, and be without a light for a couple weeks, and a chunk poorer once you pay shipping.
I just don't want to see you oversimplifying the issue by writing off critics of the fixture as just "jealous" because of what they paid for their fixtures. It's more complicated than that, most importantly, because when you are talking about corals, when you talk lighting, you are talking life support. Just like my job, you've got corals that need this equipment online.
So just make sure you cover all the angles is all.