As a general rule of thumb, a card with higher rarity will have more impactful in-game effects than one with a lower rarity
Everything from First Call to Final Installation Veneto handles the project from the first conversation through to the last fitting
Alistair, the Brigadier Alistair, the Brigadier has the same pay 8 mana ability when it attacks to buff up its army as Kate Stewart, except X is based on the number of historic permanents you control
If the triggered ability doesn't resolve (because, for example, it has been countered), the cycling ability will still resolve, and you'll draw a card
Countless collectors spend weeks hunting them down to finally complete their collection, which is incredibly satisfying and rewarding