How can you get the best out of them
It becomes a noncreature copy of whatever you choose, but it's also a mana source
In the end though, Man-o'-War was seen as the better of the two since it could itself attack and kill an opponent, unlike Undo
The first ability allows you to create a 1/1 Elf Druid creature Token, the second allows you to destroy any targeted artifact or enchantment to control the board and the final provides you with a ridiculous draw engine which draws you a card for each green creature you control
People buy boxes, packs, event decks, boxed sets, and everything else in part because they know it will retain some of its value on the secondary market
Aclazotz, Deepest Betrayal Aclazotz, Deepest Betrayal is a 4/4 with flying and lifelink, and when it attacks, your opponents discard a card, or else you draw a card for everyone that cant