Thanks for the comments guys. My goal for sound was to pick the most dense, heaviest woods and combined with the increased string tension of the 36 scale. True, Coco Bolo is a bit heavier than Ebony, but not enough to make any significant difference in sound. I guess it's just a personal preference - Macassar Ebony has that dark, mysterious quality and beauty that really turns me on.
Making a direct comparison between all my fretless basses is a bit complicated because I don't want to imply that one is inferior to another.
The Excel, with it's set neck construction, Ash body and Pau Ferro fingerboard, has alot of punch and natural growl. The neck-through Basses have more sustain and low end fundamental. ET and Black Byrd have much more of this, along with natural overtones and a wonderful, glorious chorus. I can swear they're living beings that sing. I highly recommend as many Ebony laminates in the neck as you can get; it's SUCH a unique sound, it's hard to believe there's no chorus or sustain pedals between the Bass and the amplifier. There's also the differences in sound between ET and Black Byrd due to the other body woods and electronics. ET's body has a Mahogany core with Purplerheart laminates under th Mac Ebony top and back. It's neck is Maple with Ebony laminates. Black Byrd is 100% Ebony and Purpleheart. ET has a bit of a softer edge than Black Bryd, which has a more powerful, deeper sound. Also, ET has standard Rogue electronics versus Black Byrd's Series II electronics.
I really love the sound of all my Basses. They all have distinctive voices, which is why I can't part with any of them.