the OMS that you are seeing is not the OMS of today, and DUI has had some shaky quality over the last decade as well. Their new wings have only been out for a few months, so long term durability hasn't had time to be evaluated. I have a couple of old OMS wings that have been beat to hell and keep coming back for more, but I got them used for wicked cheap.
WRT Oxycheq, they have great products and sh!tty customer service. It is the nature of the beast with their stuff, but you can usually get them quite cheap on the used market when they come up.
If buying new, it is truly very difficult to beat the Deep Sea Supply rigs for cost, quality, service, etc. For under $500 you're all in with either singles or doubles, and you get a wicked nice product. They are a requirement for me these days because of my height, which while not excessive at 6'4", when combined with a large chest, is enough that I am unable to wear a normal sized backplate without causing extreme discomfort.