The Committee II horns are very different between tenor and alto.
The altos are richer, deeper, slightly more spread but with a more lyrical and sweeter sound. They still have the typical Martin warmth and power. Slightly darker than the Committee III horns. Much better intonation than the Committee III horns...the Comm II altos have the best intonation of any vintage horn IMO. The best alto for the Paul Desmond sound IMO, but at home with many other sounds and styles. Can be used for jazz, classical, big band, etc.
The Committee III altos have more focus, more punch and power available and are brighter than the Comm II horns. That being said they're still in the middle of the bright-dark spectrum, and mouthpiece choice can really direct where they go. The early models can have wonky intonation between F2-Bb2...not all horns experience this, tends to be more prevalent on the early serial ranges. Great for jazz, lead alto, big band, funk, R&B, etc.
The tenors are kind of the opposite, intonation wise. The Comm II tenors have a more flexible pitch center and a big, resonant, warm sound with a lot of resonance and lots of volume. Much more mouthpiece sensitive than the Committee III tenors. Amazing ballad horns and one of the best tenors for pure tone. Put one up against a Balanced Action and you'd never pay the Selmer price.
The Committee III tenors are powerful, punchy, warm, and have near perfect intonation with a lot of mouthpieces. They can be played in nearly any situation and have more focus but are still very wide and fat sounding. They love to be played aggressively but are equally at home in a standard jazz setting. Set up is incredibly important on these horns, more so than the Comm IIs. Great jazz horns and probably the best R&B/rock horn on the planet.
All IMO after having owned many of these models. Remember the importance of a top notch set-up on the Committee III horns. Picky in terms of pad types, key heights and spring tensions.
Hope this helps!