I had the aftermarket set from CCOT for about 8 years, just recently replaced them with ones from wescoperformance. I think they all seem to be from the same manufacturer, the only difference is some places have more options for buckle styles.
CCOT ones worked fine, the only thing I didn't like is when I had the top off for a few months the buckles and belts faded almost instantly. Both sets I have seem to be very sensitive to the orientation of the retractor, if it's off even slightly from vertical the belts will lock up when pulling it out. It took a lot of adjusting and testing to get it just right, and even then once in a while it will still catch if you pull too fast.
The one thing I did like about the CCOT belts is the buckle mounting was very stiff, meaning you could fasten the belts with one hand without having to hold the buckle. On the newer set I bought the buckle straps run through a plastic stiffener, which holds the buckle at the right height but the end of the buckle still flops around. Also, having the button on the end of the buckle is slightly more convenient than having it on the side when you're sitting, then you can use your thumb to press the button instead of having to use your finger