| Depending on the year, the necks could be different (I'm fairly certain the Corvette $$ never came with a Wenge neck. I don't think it was introduced until after they switched to Ovangkol). If your Thumb is an older model (98/99 or earlier), it may have a Wenge neck...though popular belief would hold that it should be the faster neck.
If I had to venture a guess, I would have to say it's due to balance. The Corvette is going to be a little less neck heavy compared to the Thumb due to the Thumb's shorter upper horn. I know with my Thumb, while it doesn't do a straight dive to the floor, I do have to add a little support while playing, which could potentially slow someone down (doesn't seem to affect me much, but I'm not a speed player that much either). The Corvette (at least all the ones I've had) are also a bit neck heavy, but not as much as the Thumb, and you could probably get by with less support, and maintain a little more freedom in your movement. | 
