Standard, Commander, Modern, Pioneer, Timeless, Historic, Vintage, Legacy, and other formats are all made up of different sets with their own rules on which sets are considered legal in that format
So you want to see cards that transform into Planeswalkers or make use of mechanics that you couldnt do on a single face
Having haste on your creatures is a nice bonus, and Samut is a pretty good attacker itself
Which one you choose will of course be up to the specific needs of the current game, but it's hard to see a situation where you won't want one or the other
Here are my picks for traveling safely with your beloved Cube: Quiver The Quiver is a beauty with room for 1,000 single-sleeved cards or 800 double-sleeved cards