There just isn't any answer to the original question.
With a few exceptions (e.g., Trumpeter, Dragon, and Merit), the model companies doing business today have been around for many years. During that time their products have generally gotten better - with some notable exceptions. In the late 1970s, for instance, the hobby went through a major period of decline. For a while Monogram was operating as a subsidiary of Matell Toys, and its products were pretty crude by comparison with what it had been producing a few years earlier. Revell went through a period when it was putting photos of Tamiya and Hasegawa models on its boxes - which contained decidedly inferior kits. (I believe that one wound up in the courts.)
Today, unfortunately, many of the old, primitive kits are still being sold - and it's difficult to spot them. The Revell Germany website, for instance, shows the company's excellent 1/350 and 1/700 Bismarck kits alongside the 1/535 USS Missouri, which was first released in 1954 (and was the very first kit for which Revell itself cut the molds). By comparison with either of the Bismarck kits, it's a nondescript blob.
Revell's recent 1/72 B-17F has far more parts, and far better detail, than the same company's 1/48 B-17F - which was pirated almost entirely from the Monogram B-17G that was released in the '70s.
Another problem: companies release kits that originally were made by other companies, a long time ago. Buy a Revell Germany 1/72 B-17 and you get new, state-of-the-art tooling. Buy a Revell Germany Avro Shackleton and you get a Frog kit from the early 1970s in a nice new box.
Revell isn't the only firm that does things like that. I'm a big fan of Airfix; its recent kits are real beauties (and reasonably priced as well). But its current catalog includes two Spifire Mk.I's in 1/72 scale. One is a newly tooled kit; the other dates (I think) from the seventies. Both are packaged in nice boxes with nice, recent, computer-rendered box art. Some of the other current Airfix offerings date from the sixties.
Let the buyer beware. If you base your overall opinion of a manufacturer on one or two kits, you're liable to get snockered by the next one you buy.
There are those of us who consider these tactics fraudulent and unethical. But so far as I know, nothing can be done about them.
The web can be a big help; just key in the name of the kit you're thinking about buying, followed by the word "review." You'll probably get sent to several knowledgable reviews of the kit - but no promises.