Thanks to mythic rarity, card prices trend and behave much differently today than they did pre-Shards of Alara. One of the biggest differences between then and now was that, pre-mythics, mana-fixing lands all commanded double-digit price tags. Probably the most infamous example is the Ravnica-block shock-lands—when they were Standard-legal the first time around, the pricetag for them hovered around $15-$25 apiece, depending on the land. Ravnica ones were worth a little less and Dissension ones were worth a little more, simply because less Dissension was opened. "Third sets" were always the worst.
Now that mythic rares absorb the lion's share of a set's finite value that used to be spread more evenly among all the rares in a set, stuff like, say, a rare cycle of lands aren't worth quite as much now as they used to be. Which is good! Spending lots of money on cards you don't even cast is a tough pill to swallow for new players especially, but it's necessary in order to have a functioning deck. I mention all of this because the Vehicle Rush Challenger deck needs a serious land tune-up. As it exists, Vehicle Rush is less deck than "frustrating FNM waiting to happen."
The conventional wisdom about Rivals of Ixalan Standard states that there's no reason to play Mardu Vehicles; Mono-Red Aggro is a thing that exists, it executes a similar gameplan, and what you lose in explosiveness you more than make up for in consistency. However, if crewing up Heart of Kiran is your thing, then this is the deck for you.
If you're committed to crewing up vehicles and this deck is your starting point, my suggestion is to pick up more of the Kaladesh dual-lands. Concealed Courtyard and Inspiring Vantage are pretty much automatic four-ofs. From there, it'll take some tuning and tweaking to figure out what other lands you want to play.
Depala, Pilot Exemplar is the easiest spell to cut in the deck, in favor of some mix of Hazoret the Fervent/Rekindling Phoenix/Walking Ballista, but there's no rush. Getting the manabase squared away should be your highest priority. That's going to sound lame to a lot of players just getting started with the game, but that's just the way it goes. Can't ignore the fundamentals.
That's what these decks are about, after all: learning the fundamentals of the game. Even if we accept the "Mardu Vehicles is a worse Mono-Red Aggro" premise as true, these decks aren't about optimal deck selection. They are a way for new players to not have to start their progression through Organized Play from scratch.
Examining the ways WotC has tried to get new players started in the past, it's clear that they've always wanted players to experience Magic at a slow pace. Figuring out that cards like Nourish are bad usually involves sticking a bunch of life-gain spells in your deck and subsequently losing a bunch. The more stubborn the player, the more losses they require. The life-gain card example is a broad one, but the point is that evaluating Magic cards is an ongoing process and the folks developing these introductory products would rather provide players with a product that encourages the development of an internal framework for sizing up cards. If the starter deck's too good, it's the equivalent of answering the question "why is this card good?" with "because it's good."
What makes me so happy about the Challenger decks is that they represent a shift in WotC philosophy. A firmer guiding hand in getting new players to understand tournaments is a good thing, and Challenger decks are the Crystallization of this realization.
The Second Sun Control write-up's coming Thursday. Sit tight.