I've been thinking about cars a lot lately.
I'm going to put down my thoughts on what matters and what does not when it comes to a car, in terms of how much most people will like owning it, and what it will cost.
What doesn't matter
Fuel costs often don't matter. A Prius is (surprise) the most efficient vehicle sold in Canada. According to that metric, it would cost about $760 to drive 20,000 km, using a locally optimistic $1/l gas price. By comparison, the best full-size car would cost $1600 (Hyundai Sonata with a manual transmission).
One of the worst cars, economy-wise, is a Chrysler 300 SRT-8. It's a shade under $3000/year. Money well spent, I say, considering that car can carry five in comfort plus a good load of luggage and has more horsepower than every car I've ever owned, COMBINED. And I've owned four cars.
The point is, these are the radical extremes of passenger cars, bought new. A mundane Yaris costs about $1240 on this metric, and virtually every other car most people will shop for will fall between these extremes. So most people in most situations can save about $100-200 in annual operating costs by buying an especially efficient vehicle. This is probably about the same as the difference between getting lucky and unlucky in your maintenance costs.
Horsepower doesn't matter. Look: I love powerful cars. My dream machine is a 550-horsepower station wagon (something which, astoundingly, is a real thing). But if you are buying a car to get places, the horsepower won't help.
In my darkest moments, I would suggest horsepower doesn't even aid in the measure known as "fun to drive." One of the most entertaining cars I've ever driven was a rented Hyundai Atos hatch with a 1000cc motor and a manual transmission. The secret was to keep it on tiny twisty roads, where it was a pure fun-machine.
Sat-nav doesn't matter. I don't say this because GPS systems are a bad idea. GPS systems are a GREAT idea. If you've never tried one, you ought to. They're brilliant. However, the built-in sat-nav systems on almost every car that offers them range from moderately behind the tech curve to hopeless and unusable. There's no reason to subject yourself to the tragedy of an expensive built-in GPS when the latest TomTom (or smartphone car cradle...) is both cheaper and far better.
What does matter
Repair costs (and to an extent, luck) matters. The issue is that repair costs aren't like gas bills: they're not predictable. The key here is to have a contingency fund for repairs, because...
...Buying used matters. Do the math: if you buy a few years old, you generally get a car that is functionally the same as it was when new, only for about 2/3 of list price. Indeed, check out this rather intriguing article explaining the depreciation plateau for cars that are 2-5 years old. Verry interesting!
The point here is that buying a car that's not new risks a big off-warranty repair, but puts tens of thousands of dollars into your pocket up front. So you need to budget for repairs so you can properly enjoy your savings.
some Mod-cons matter. And are a good reason to buy used. Air conditioning is an obvious one (though it's pretty rare to find a car that doesn't have it nowadays). Keyless entry was one that surprised me: like AC, before I had it, I thought it was a nice-sounding but superfluous feature. After, it made me really want keyless entry for my house. These features tend to add less to the price of used cars than they cost as options on a new car.
NVH matters. That's "noise, vibration, and harshness." It's the industry term for making a car that is quiet at all speeds, and doesn't crash and judder over potholes. Believe it or not, it's this (and not leather or roominess or dual-zone climate controls) that make luxurious cars feel luxurious. I am now on a quest for the quietest, most solid-feeling small car made. Any suggestions?
Beyond that, what matters is obvious: if the seats feel nice, you'll be a happy camper. Considering how mixed the reviews for some cars' seats can be, I think this has a strong element of personal preference. A certain steering feel probably matters, but since car magazines and blogs already describe that aspect of cars with the wacky faux-precision of oenophiles smelling wine, I hardly need to discuss it.