I'll give my personal opinion of older American saxes. And keep in mind I like Rocksax which means for me; to play loud. A player that is into jazz- or classic-saxophone perhaps have other opinions.
Of course it’s you as a player and your mouthpice that does most to the sound. I have joined the group of saxplayers that thinks that the character/sound/tone is determined by the neck, tube/taper and the toneholes placement on the tube. Between the toneholes geometrics are established and that makes sound/tone of the saxes. The way the toneholes are made can also give the sax a differnt tone. The angle of a soldered tonehole (Martin) is different than a drawn tonehole. So thick wall – thin wall, plated – bare brass, rolled toneholes – straight toneholes …. . It doesn’t matter that much, or ... ??
Beuscher: Great players. Allround sax - load screaming Rocksax, sweet jazz balladas or classical pieces ... . The Aristocrat model (late 30' to early 50's) and a 400 is the best Beuschers. The Big B and a 400 with underslung octave keys are my favourites. Even Bueschers from the 20's are nice. The straight soprano model LP 122 True-Tone is a fine soprano. Beuscher also made a straight alto. Hard to find. Beuscher was bought by Selmer USA in 1963. Beusher made sopranino, C-soprano, B-soprano, Alto, C-tenor, Bb-tenor, baritone and bass saxes.
Conn: Overall a high quailty sax. The best Conns were made in the 30's or early 40's. A 6M, 10M or12M from the 30's are very good. Allround saxes. There is a big difference between a Conn from the 20's and one from the late 50's. Conn made sopranino, C-soprano, Bb-soprano, F mezzo soprano, F Conn-O-Sax, Alto, C-tenor, Bb-tenor, baritone and bass saxes. In the 60's Conn, more or less, concentrated their production to student saxes. But they kept a small production in Elkhart. The Conn bari to low A from 68-69 is a result of that.
King: The King Super 20 is one of the best saxes that has ever been made. The best Super 20 is from 45 to the early 60's (H.N White). The double socket neck is great. They made saxes with silver necks and silver bells. Loud saxes. Jazz saxophone but also fine in Rock 'n' Roll. The production of the "real" discontinued around -75. But Super 20s could be bought in the 80's as well. The late super 20's are not bad but they should be a lot cheaper than a Super 20 from the 50's. The Super 20 and Zephyr Special is roughly the same sax. Even the Zephyr model are fine saxes. King made. C-soprano, Bb-soprano, Alto, C-tenor, Bb-tenor, baritone.
Martin: This is my favourite sax! I don't say they're the best. They just fit me perfect. Jazz, R&B and Rock'n'Roll sax!. It was used in the classic world as well. The Handcraft (Comm I &II) and the The Martin .... (Committee III) are the best ones. Flexible horns that can work with most mouthpieces. The Committee II, and some Commettee I have solid silvernickel keys. Very durable. The RH thumbrest is adjustable. All Martins have thick walls with soft soldered toneholes. The soldered on toneholes are not only good. Read Stephen Howard's website! Martins have good intonation and The Martins neck is probably one of the best std necks that has ever been made. Martin developed their saxes and made them more contemporay to the bitter end. Martin alslo made, as far as I know, the first American low A. It was the Magna bari. The Magna model was the top model but I think the ordinary The Martin is nearly as good as the Magna. Martin made C-soprano, Bb-soprano, Alto, C-tenor, Bb-tenor and baritone.
Most manufacturors except Martin had underslung octave keys as an option (Super 20 Conn 10M and Beuscher 400 tenor). The had braces on some necks. A brace make the neck more stable/less fragile. Are the necks with underslung octave keys less durable?
As I wrote earlier, I'm not a real expert on saxes and I can be completely wrong!!
Thomas