Since it only lets you keep the mana as steps end, not phases, you cant carry it into your main phase two
Good cards which are playable in both types of format keep your collection flexible enough to play a variety of ways
Otherwise, you can draw a bunch of cards (always good) or scry a bunch of cards (also good) to get back to it faster, things I dont mind doing because, you know, theyre good
For instance, consider the following Legacy deck that really would not need to do much to transition to Modern: Creatures (29) 4 Lord of Atlantis 3 Merrow Reejerey 4 Silvergill Adept 4 Cursecatcher 3 Cosi's Trickster 3 Phantasmal Image 4 Master of the Pearl Trident 4 True-Name Nemesis Lands (20) Spells (11) Daze deserves an honorable mention as well, only narrowly missing the Top 25 list
Faced with fierce competition, bombarded by stardom, and confronting dangerous schemes brewing around her, Chandra is determined to race for Nissa's future