Basically, the top three are fairly interchangeable but worth a meaningful amount more than the bottom two, based mostly on the relative value of the reprints in each deck
Given how expensive spells get as the match wears on, that can be a big, big hit
Each Zendikar Rising Collector Booster contains 15 cards and 1 foil double-sided token, with 1 foil alternate frame rare/mythic (Expedition, showcase, borderless, or extended art), 1 foil rare/mythic, 1 non-foil borderless or showcase rare/mythic, 1 non-foil extended art rare/mythic, 1 foil showcase common/uncommon, 2 non-foil showcase commons/uncommons, 2 foil uncommons, 5 foil commons, and 1 foil full-art Basic Land.
Mmmenon, the Right Hand is a great Urza stand in for lower Bracket play
To cast a Turn 2 Karn, you need two pieces of fast mana, two lands, a zero-drop creature to enable Springleaf Drum or Mox Opal, and the Karn itself