This conversation is fascinating to me, because these two mechanics are more-or-less implemented in the Mox Cube. Having 10 moxen basically means you start at 2 cmc in expectation (which makes 1 drops less value and 3 drops more valuable). This has definitely changed which cards I consider "efficient" - in much the same way that 4-drops are borderline unplayable in Legacy, but in Vintage,
Arlinn Kord (for example) is absolutely respectable. Even more directly relevant, cost reduction in my cube is omnipresent. With familiar- and helm-effects running around, it's very common to have your relevant spells discounted.
With the combination of the two factors above, one thing became abundantly clear to every drafter very quickly:
Elvish Visionary is a bomb. I run the Zealot, the Wall, and two Visionaries. These cards are
hotly contested during the draft. One issue with the moxes is you basically get fewer looks at drawing each additional land drop. The turn 1 Visionary becomes a quintessential smoother (that decks can later go on to abuse with blinking,
Erratic Portal, sacrifice effects,
Earthcraft, etc, etc).
But when Visionary costs 1 mana later in the game, the blinking and replaying will draw you a lot of cards at extremely efficient rates. Especially when re-casting is involved, a 1-mana Visionary several times a turn (often with
Beast Whisperer in play) drives the storm count up real quick for a RG Grapeshot deck or a GW Atherflux Reservoir deck. The incessant card drawing with discounted creatures does also tend to make their library disappear at astounding rates with
Psychic Corrosion.
Overall, the equations for speed, efficiency, and explosiveness change drastically. Although I should add, it's not clear how much this is due to the extra land drops and the cost reduction itself. The surrounding environment is also dedicated to letting you cast as many spells per turn as possible and maybe it's these support pieces (the
Paradox Engine's, the
Kor Skyfisher's, the
Beast Whisperer's, etc) which cause the perspective shift.