Comparison One: Equipment
The thing I have seen Vehicles compared to most often are Equipment. I think this is largely from a conceptual level - both are artifacts, both require creatures to do anything, both take two cards to make one larger creature, both represent tools which augment a person/creature's ability to perform tasks, especially from a real-world perspective. But while there are a number of parallels, there are also a number places where the comparison doesn't really work. The most obvious is probably that, once you cast the Vehicle, it doesn't require more mana to do its thing, rather a creature. Also, with a vehicle, the only attribute of the 'base', small creature that matters is its power.
But the biggest difference comes when an opponent kills the combined giant monster. With equipment, you just move it over, and presto change-o, you have a new giant monster. Or, at least you did back when they would print substantial buffs on equipment, from cards like Vulshok Battlegear or Vulshok Morningstar. Because that was such a huge advantage, so hard to beat, they've generally stopped doing that - equipment tends to be much weaker nowadays. (Similarly, you used to be able to move equipment to have effect on both attack and defense, but that's dampened by weaker equipment and higher equip costs).
You can't do this with vehicles; kill the vehicle, you're left with [a] smaller creature[s]. And that's it - there's no way to go big again. So of course, this makes vehicles in some way inherently 'worse' than equipment... except that R&D understands all of this, so the development team has thus balanced the cards... accordingly? It remains to be seen if they're actually stronger or weaker in practice, I suppose, but the point is that you actually need to look at the rates on the cards to know for sure. Gaining Life is 'inherently weaker' than doing damage, but W for gain a billion would be stronger than Shock.
Comparison Two: Bestow
So bestow also has many similarities to vehicles - again, you're using 2 cards to make one bigger creature, investing a reasonable amount of mana to get this, but in two chunks. And in this case, if you kill the big creature, you're left with a small one, just like is the case with vehicles. This analogy still has the smaller creatures total attributes mattering though, which is still different from how vehicles work.
Comparison Three: Emerge
The last comparison I'd like to draw is with Emerge creatures. We just saw these, of course, so they're fresh in everyone's mind. And once again, we're using two creatures, and a requisite amount of mana split into two chunks, to get one large creature in the end. Emerge is a better analogue to vehicles in the sense that, in the end, your big creature is just what's printed on that big card. But vehicles lack the on-cast triggers of emerge cards, and Emerge creatures, when killed, leave nothing behind. They do, though, point out nicely that how the cards are balanced by the development has the biggest impact on the cards' strength, and not just the inherent mechanic. If the emerge creatures didn't get you card advantage from their cast triggers, just putting two cards in for one big body would be pretty bad. But they did give us these effects, and the cards turned out strong.
So I think all three of these provide decent analogies for Vehicles, but as I said at the top, none are perfect, and you really need some independent analysis to go on. I'm going to try my hand at this, but I do want to note that I'm going to be talking about general/generic case here, which applies more to limited than anything else - in constructed, you're obviously only aiming for good case scenarios.
The first thing I want to note here is what I'm calling "Effective Power" - on a board where your opponent has no creatures, your vehicle is hitting them with only their power minus their crew cost, since you have to sacrifice attacking with that much power in order to animate your vehicle (best case - sometimes, you sacrifice more). When you do this subtraction, their at-first-gaudy numbers start to look significantly worse.
On the flip side, of course, when you're squaring your vehicles off against opposing creatures, they still trade with the full force as printed on the card. In this case, they're an excellent deal. Thus, we get to a simple conclusion/motto: with vehicles, trading is good, racing is bad. (No, the irony that vehicles don't want to race is not at all lost on me).
Still, this isn't exactly a huge secret, so of course when you're playing against vehicles, you'll be working cross-purposes to that. When someone activates a vehicle and attacks, the best response is generally going to be not to trade with it, but either take the damage, or chump block. Attacking with a vehicle is going to open up a weakness - you're tapping what's probably a significant portion of your board presence, leaving yourself open to a crack-back; this kind of play leads to, you guessed it, racing (so the flavor isn't all lost, I guess?)
So in order to get advantage with vehicles, you have a few options:
- Be so far ahead that they HAVE to trade/can't race
- Have the board so clogged that they can't crack back
- Use them on defense more than offense
Of course, I would be remiss to not note that the Development team has understood this play pattern, where vehicles tend to inherently be better on defense. They have compensated for this by giving very many of them offensive-minded abilities. Trample, Menace, Haste, Attack triggers, blocking restrictions on opposing creatures... even flying is generally more useful on offense than defense. Look at the vehicles in the set, and you'll see that a huge percentage of them have something like this, and you'll see it's pretty clear that there is this inherent defensive nature to the subtype. These inducements will probably make it right to attack a lot of the time, but they of course won't always. And it's extra worth noting that, on the few vehicles which don't have these kinds of incentives, blocking is going to be the go-to way to be.
To learn more, you really need to look at individual cards... but that's a separate post.