I picked up a DCT 15000 for my return last year. At first unbox it seemed well built, heavy, and worked. I used it to test initial plumbing because the plan was to use it as the primary return. It moved a lot of water and it was pretty quiet. I was removing it to move the tank into the house, disconnected the union, and then used the handle it comes with to pick it up and move it. The handle broke off. Not a huge deal I said to myself but I found it odd. Why add it if it isn't strong enough to hold the weight and be carried by it. Anyway strike one.
After setting up the tank inside the house and reconnecting it to the plumbing in the sump I noticed a bit of separation on the neck and body. Disconnected it again, pulled it out form under the tank and sump, and sure enough. The base neck on the outlet was coming apart from the body. There is really no way to repair that. I removed the union I was using and felt inside the pump and can see why everything was breaking. Paper thin plastic on the body. Ok, strike two.
This was about the time of the public release of the first batch of Cor 15 and 20's so I got a lucky order on a 15 and picked one up. I immediately compared the bodies and neck area and it was night and day different in thickness and overall quality. Strike 3. Gathered up all of the DCT's cables, controller, and into the recycle electronics bin it went. Cor 15 has been rock solid. So much that I picked up a 2nd for my skimmer and now considering a 3rd to power another pair of sea swirls.
I've owned some RW4 and 8's when I had a 40 breeder and they worked well with my Reef Angel controller. Any of the flow patterns worked great and they lasted about 2 years. One I had to replace around 18 months in but may have been attributed to a snail. In any case the only complaint with these are that they have a pretty high and noticeable fall off when dirty. So I had to be sure to clean them at least every three to four weeks otherwise it was drastic.
So not a huge fan of the products especially of the return pumps. I would avoid them but this is just based on my experience. Your mileage may vary.