Shadowy Houses

What’s the difference between “The Tower of Knives”, “The High Castle” and “The Windward Tower” houses? They’re all Shadowy houses and allow you to hold 3 cards in your hand. So why is the first one available at Shadowy 10, the second at 30 and the last at 50? There must be some differences, right?

Thanks in advance.

The number of Certifiable Scraps you get from them. The Windward Tower gives you 2, the High Castle and Tower of Knives only give you 1.

Thank you.

The other non-Certifiable Scrap options tend to be more valuable as well as the X requirement goes up, usually worth more Echos or give more Connections than the ones with the lower requirements.