My take on this question:
- If you want, try it, you might like it (or not), but either way if you are intrigued by it it'd be fun.
- The wide neck thing and fatigue can be a real issue for some players - I have big hands and found that even 5 string basses were a problem for me if playing for long stretches of time.
- Anthony Jackson is a monster player who has obviously worked hard for years to master his instrument. My experience with most 6 stringers that I hear out there is they've just picked one up and spent a little time fiddling with it, and are not usually very tasteful in what they do with those all of extra notes.
- Alot of what I hear from 6-string players (including the incredible solo above from Mr Jackson) really sounds more like a deep guitar to me than bass. I'm still more of a "bass is a rythym instrument" kind of guy, and to my ear, some sixers lean more towards flourish-style playing at the expense of holding down the bottom. Not to say that a great player couldn't do both but that has not been my listening experience.