There's more to build quality than materials used. How they fit together, how they are machined/molded, how it all holds up. Both BMW and Kia use plastic in their cars, but the fit and finish on a BMW is much better.
The hard drive bay in the front of the Eleven Hundred is two sheets of metal with small holes cut out between each drive bay. That's two sheets of metal that completely obstruct airflow. With the Arc, you can remove one half of it and still have plenty of room to mount HDDs/SSDs while having a less obstructed intake. With the 690, you can reduce it to the exact number of trays you need.
While the negative pressure might not seem like a big deal, if you buy two 120mm fans at lets say $8 a piece, that increases the price by $16, making it an even worse value.
The H100 is pretty popular, and it's a closed loop watercooling system. To mount a standard 240mm radiator, you need two 120mm fans with 15mm spacing between the two. This is a pretty standard feature. It seems as if it was a specific omission to prevent their customers from spending money elsewhere when they have their own Kuhler series. Hate that kind of practice.
The missing grommets are the ones above the motherboard tray, next to the roof. They didnt allow proper spacing for the standardized holes, and as a result, probably couldn't source the right size of rubber grommets without increasing the price of the case.
If you really really want it, and think that I'm trying to be combative, please let me know. I will relent