are "LONDON" pressings made in the UK, inferior to the Decca pressings


Are "LONDON" pressings made in the UK, inferior to the Decca label originals of the same record? Anecdotally
 I 've heard mixed responses to this. Anyone have a lot of evidence , having heard both?
rrm
Hello edgewear,
If your first post is indicative of what you have to contribute, future posts will be much anticipated and appreciated. 
Charles 
Some general info for better understanding

Decca SXL made the very best recordings (from the Team, Hardware and from general understanding...Mercury is a different chapter) from the music repertoire we can listen today.
Decca was extremely careful not to get bad customer feedback (distortion, overdrive, don’t forget, those were different times from cartridge design- round diamond tip - ...) and SXL was a sale on commission!! Unsold records came back to Decca and were melted.
That is the reason why they are so expensive today. Simply limited Quantity.
Sound is - or was - first rate. I think, a Benchmark which was never surpassed for their Titles.
Those Stereo SXL were very expensive in the early 50’s and it was pure luxury to get those after the war, the Economy was still down.
In USA there was a similar economic situation but fixed pricing was cancelled around 1960.
London CS was created from Decca because Decca couldn’t use their own name in USA.
(There was a small private label which was named Decca). To avoid any problems, Decca decided right from the Start to create for USA a new Name, London.
Now for the "Sound"

For both Labels they used the same Mastertape.
But the main difference was - or is - the Peak of the cutting process. Decca thought, the US listener expects a different kind of sound, the result was a ~ +2dB Peak in the cutting.
This means, a distortion in the headroom was accepted.
But this is rare, those Decca Cutters were real artists, unsurpassed. But they can sound a bit different based on that (depends on your ears and quality of playback chain).
Next difference, Decca thought that USA wants something "Physical", means, thicker LP’s.
For Londons they used 20gr to 40gr. more vinyl. This varied a lot 1958/1959 and became Standard from 1962 (∼ 205gr). When you compare such records (SXL / London) you should use a Arm with VTA adjustment. This is mandatory.
It is a very interesting chapter for a curious audiophile, because we have different diamond cuts in our carts and that will make a huge difference when we talk or rate such records.
Also, not every SKL was available as a London CS and reverse. And of course, completely different Prints onto the Box.
Decca was also very open for information transfer, they had a good Management and later a Partnership with RCA (Living Stereo) to do their European recordings. RCA was happy because those sessions were way cheaper than in USA (affiliated unions).
A class on its own again...but this is also a different chapter.
Syntax,
Interesting points that in summary do not dispute or contradict the gist of what edgewear has posted.
Charles 
@syntax
"London CS was created from Decca because Decca couldn’t use their own name in USA.
(There was a small private label which was named Decca). To avoid any problems, Decca decided right from the Start to create for USA a new Name, London."

From Wikipedia, fountain of all knowledge:

Decca Records is a British record label established in 1929 by Edward Lewis. Its U.S. label was established in late 1934 by Lewis, along with American Decca's first president Jack Kapp and later American Decca president Milton Rackmil. In 1937, anticipating Nazi aggression leading to World War II, Lewis sold American Decca and the link between the UK and U.S. Decca labels was broken for several decades.[1] The British label was renowned for its development of recording methods, while the American company developed the concept of cast albums in the musical genre. Both wings are now part of the Universal Music Group, which is owned by Vivendi, a media conglomerate headquartered in Paris, France. The US Decca label was the foundation company that evolved into UMG.

@syntax I fully agree with you that the Decca engineering was the top of the foodchain back then and these recordings are rightfully considered a benchmark even today. Their consistent high quality level was not approached by their competitors, although there are titles in the Mercury, RCA and HMV / Columbia UK catalogues that are equally good, but more 'hit or miss'.

Your suggestion that the London CS were cut differently than the SXL's is an urban myth perpetuated by SXL protagonists. There's no evidence to support this. Quite the contrary, the test pressing slip is convincing proof they were created equal. Why do you insist in keeping this story alive? You don't have to worry about your investment. The snobs will make sure this remains safe.

But don't take my word (or a Decca test pressing slip) for it. The best and certainly most enjoyable (if you're unbiased) way to prove it is by comparative listening. I've compared dozens of near mint SXL's and CS's with identical matrix, mother and stamper numbers. A great example is the Albeniz Suite Espagnola (generally acknowledged as one of the prime Decca's). Comparing the SXL 6355 and CS 6581 - both with 1G matrix, first mother, B stamper (the earliest) and JT tax code - will tell you all you need to know.

Also, where do you get the idea that the London's used heavier vinyl that SXL's? Decca wasn't particularly consistent with vinyl weight, although it is true that the earliest pressings from 1958 (the so called pancakes) are much heavier. But variations in weight existed within both labels and had nothing to do with either the Decca or London label being attached.

I honestly don't think it is fair to project modern marketing tactics like 'limited editions' (or limited quantity) to Decca's way of doing business in the '50's and 60's. If they were so concerned about quality control and even melting unsold copies (?), why did they reissue older recordings in the budget SDD Ace of Diamonds series, using the very same (and by that time well used) stampers? This was common practice and Decca was a company like any other in the business of making money. They were the best in the business and  don't need these kinds of 'imaginative' fairytales to 'pique their mystique'. That they reached this high quality level using normal business practices is - if anything - an even greater achievement!

So by all means enjoy them as some of the best records ever made. If you enjoy them more with the SXL label on it, go for it. They sound great! But my intention was to give unbiased advise to (apparently) a novice collector who is interested in sound quality, not status. In the current marketplace you can buy as many as 10 London bluebacks for every SXL 2000 series with the same sound quality. Not a difficult choice if you ask me......