Re: Most popular jazz saxes.
One of the most popular jazz altos and my personal favorite is the Conn 6M. Many artists, including Charlie Parker, have used the 6M. They have a great tone, and they play very easy. I really like Otto Link mouthpieces. The set-up I use is a 1950 6M (without rolled tone holes, with metal resonator pads) an Otto Link Tone Edge 5* hard rubber mouthpiece, a Rovner Dark Ligature, and Rico Jazz Select unfiled reeds.
Other vintage saxophones I would suggest trying are the King Super 20, Buescher 400 Top Hat & Cane, and Selmer Mark VI. Of the new saxophones I would recommend trying the Yamaha 82Z, which is very bright and also plays very easy, the Keilwerth SX-90 and SX-90R which has soldered on tone rings similar to the rolled tone holes of the vintage Conn saxophones, and I would also suggest trying a Cannonball. Some of the new Cannonballs are finding favor with pro players, and the quality has gotten considerably better. Of course, there is also the Selmer Ref. 54, which is said to be based on the original Mark VI.