Well, it has been a difficult effort - much more than anticipated. Without further ado, here's my thoughts on diecast vics in wargaming...
First it is unusual to find a line of cars that are actually all the same scale. What the manufacturer does is say "1:43" and many of the cars are. But all the cars are the same SIZE, which is to say about the same dimensions. So a Mini or Fiat 500 will be about the same size as a full-size truck, which means it is NOT the same scale as it should be much smaller if it was actually 1:43. This is a common problem with nearly all the popular lines, and has to do with the manufacturing process no doubt.
So, right off the bat you have a problem - the scales of cars in the same line by same company do not actually match up, only the sizes do. This means you have to shop around and even carry your 28 or 25mm figs with you. Interestingly, a big vic in real life - say a large SUV - in a smaller scale may actually match up in size with the sub-compact made in a larger scale. So a 1/64 SUV may match up with a 1/55 compact.
The toy industry has its own priorities, and if you go for 20mm or 1/72 or 1/76, you are probably going to find plenty to use one way or another. 20mm figures are out there, and there are plenty of nice ones, so I recommend that if you want to fit into a tight battle space. 15mm is also no big deal, you can probably start using Matchbox cars at a $1 each.
If you go for 1/48, that is quite close to 1/43 and you can probably find a lot to use. Only problem is that the game starts to need a lot more table space. For skirmish games, a cluttered area is great as it provides lots of cover. But the vics quickly get big enough to be more like houses, and then the houses look small because they are often undersized. Undersized houses are needed because they become mountains when correctly scaled with the figures. Again, just something to keep in mind - do you want a large obstacle in the middle of your game table? Or will figs be able to fight within the building?
If you are looking in the most popular skirmish rule scale which is 1/56 to 1/60 or so or 25-28mm [-ish] then you gotta dig around harder. Toy plastic or metal cars in this size/scale are a lot less common. Siku brand is 1:55 and from Germany, therefore available in the EU. But they are almost unavailable in the USA as they are not exported here - something to do with safety regulations. Buying them on line and shipping them over puts the into the $15-20 range quickly.
The popular 1:43 scale Chi-Com cars are quite frankly too big. They make most 28mm figs look like kids getting into a car, and take up a lot of table space. Plus, they may not fit into your terrain like roads and parking spaces unless you bought / created it to match them.
As I subscribe to the theory that terrain almost always has to be shrunken a bit due to scale considerations, generally speaking terrain pieces should be a bit smaller than in real life. So, if a building would be 8" x 8" in true scale, it should probably be 6x6" in a wargame, or else it dominates the game space. This is a good rule of thumb to keep in mind unless you want to do the math of scale distortion.
What "looks right" ultimately has to trump any other decision. A parking lot full of cars is a "terrain type" and shouldn't be represented exactly in most games. So... what looks right??
Well, cars that are scale correct or a bit smaller. And that means the car should be about 25-30mm wide in 25-28mm, and about 50-60mm long, for most day driver compact cars. A few are larger, several are longer [the width of a vic is set by road / parking space / bridge widths, etc] but generally speaking, most of us drive a car that is less wide than we are tall, and 2-2.5 times our height. You can look up the 20-30 top compacts in various formats and that's about what their dimensions are.
So... what is the right choice as "scatter terrain" for urban warfare?
Generally speaking, it's a car that is smaller than 1/43 - it's more like 1/60.
Below, some trucks I got at the grocery store: a military truck, and an old-school farm / dump truck. They were $6 apiece [thus giving its Chi-com manufacturer a mere $5 profit] but just the right scale for 28mm, IMHO. So I took pics:
Below, another approach - buy and/or build the mat / table, then build / buy the terrain. The parking lot sets a visual tone for the game. These Deep Cut Studio mats are about a bit tight for 1:43 - the middle red car with the stripe is tight in the space and it's a sub-compact. The top red car is better, but perhaps a bit small, and it is a compact. The pickup truck and the Army truck are just right. But nothing is perfect, including these mats from Lithuania.
1:43 diecast. It's a bit big - altho a Suburban size truck is quite large, this just doesn't look right on the table. The proportions are off.
side-by-side, not too different. But the blue has a lot more "mass".
Here, by comparison, the Mondo Motors car looks much too large. Crazy next to the bus, and obviously too big next to the army truck.
The farm truck scales nicely with the army truck.
The Kidami fits in - looks just right.
Below, a group of Kidami pics.
Closer - might even be a tad big.
This wagon looks a bit small next to the bulk of this guy. Then again, Soldiers look a lot bulkier with their gear and weapons, anyway.
"you cut me off, dog!" "Take this, swine!"
Hopefully, this post will save you some time should you decide to buy some diecast yourself. But overall, switching to 20mm is probably the easiest thing to do. But they are a bit small for my aging eyes, so 28mm it is!