Updated: March 2023
One of the primary aims of Yesterday's Airlines is to help educate collectors, giving them the information they need to make decisions they are happy with. I'm not necessarily telling you what to buy but hopefully helping you to make decisions for yourselves by providing as much evidence as I can.
As discussed here since the level of quality between brands is so close and the line between success and failure so thin it only makes sense to look at the mould being used by that particular manufacturer for the aircraft type. This is where the major differences lie. Everyone has good and not so good moulds and often there is very strong competition between brands for certain aircraft types.
It is regularly asked 'who has the best X' and often there is a general consensus in the hobby as to the answer, however the answers to these questions are usually glib and unsupported by evidence. If someone asks what is the best 777-300 mould for example it’d be useful to a) know what ones exist and b) to actually look at a proper comparison. 
Hopefully this site is a good resource and therefore i want to bring together all the information I have created and gathered in a central spot. This is that place. You don't need to necessarily agree with me but you should be able to provide sensible counterpoints if you don't.
I am sometimes accused of bias, usually by people with their own massive and poorly hidden agendas. I am biased - towards high quality 400 scale models. I am interested in the politics and business shenanigans that go on behind the scenes but they rarely influence my purchases and they shouldn't influence yours. This website looks at the quality of the models and that is also what you should do. Everything else is noise.
RESOURCES​
This site contains four main areas of content to aid decision making and I will link to those were appropriate. Broadly they are:
A type by type examination of all the moulds that have been made for an aircraft with some basic information about quality.
A detailed look at the active moulds for specific types scoring them on a variety of categories to determine which comes out on top.
Reviews of individual model releases scoring each out of 30. One third of the review and score is dedicated to the mould.
I regularly am sent new mould samples, from the more enlightened brands, prior to them going into production. I always give them a thorough lookover at the site.
BEST MOULDS
There are lots of different aircraft types and available moulds so for ease of reading I've created separate pages for each of the major aircraft manufacturers. Typically in 2023 it is the extant manufacturers producing the best models, but there are still examples where older long extinct brands retain the best mould for an aircraft type. Read on to see who I think has the best moulds and why: