I own both a
@Marshydro FC-4800 and an FC-6500 and love them both. I mount the drivers outside the tents which leaves it incredibly cool inside the tents which is VERY important to me. An important buying decision for me is warranty and Mars Hydro has a very good warranty. Not sure how reliable a warranty would be for an LED light purchased from Alibaba. Not saying it wouldn't be good, but for me it would be suspect.
I do want to add that I use my FC-4800 in a 3x3 tent and have never had the dimmer set to higher then about 75% of full power so I feel it would very nicely power a 4x4 tent. That is my 2 cents FWIW.