IOW a tube or a bottleneck?
I get this question often from people who want to start experienting with slide playing.
Well let's see... You can get used to anything AFAIK, and really: I've seen people who have adapted their skill and style to the gear they chose ages ago.
However, those early choices are usually circumstancial, very rarely they occur with predisposition.
All that is great to know but it doesn't help you pick, does it? So I can start by admitting I own both glass and metal slides. Not because I can't tell the difference, but because I think each may be suited better for some styles or guitar setups. I will attempt a brief description of what I consider pros and cons of each and hope this will help you decide where to go.
Right. Like the picture says, I think metal slides are great for acoustic or resonator setups. Especially with steel guitars - like my National Delphi - you seem to get a fine sound that brings out the character of the steel body instrument.
Great for playing early blues like Robert Johnson, bluegrass or ragtime with a southern twist, New Orleans rythms and basically any sort of roots of music reference is greatly supported by the attack of a metal slide on open tuning .13s.
This is especially true if you're wearing the slide on your pinky like this guy in the pic. Usually purchased glass bottlenecks for the pinky are rather thin and lightweight, which poses a problem for .13 gauge on accoustic setups. You feel like you're missing the weight that will force your tone and pitch where it ought to be. I own a thick bronze pinky slide and it really brings the weight on the strings without stressing your wrist. Even a thinner metal slide, though, will compensate for the lack of weight by its harsher sound. It somehow sounds louder on bronze than any glass slide.
Some people play electric with metal slides. You see Johnny Winter with a metal slide, Joe Bonamassa doing some impressive slidework on high gain electric, and many more. In my opinion glass sounds better on electric, however, different players have different tecniques, noone's wrong or right. Perhaps if you gt used to one type of slide you don't feel comfortable with the other and prefer to push your gear to the limit rather than swim to the other bank.
Another issue associated with metal slide is fancy. Ie everyone in the back row will see your slide flashing on stage whereas glass bottlenecks seem to go visually unnoticed.
More accurate than metal slides because a) they are lighter (for the same thickness) so you move up and down the fretboard more precisely and b) Real thick ones which allow for better damping control are easier to come by than in metal.
The overall tone is not as loud or rough as that of a metal slide, so you may find that acoustic setups work better with metal. But for electric the glass comes in real handy. Many electric masters like Ry Cooder or Bonnie Raitt play with bottlenecks.
Glass bottlenecks are easier to experiment with also. Many build their own. Bob brozman still plays with his favourite bottleneck which he claims to have made himself when he was 13 or so.
For me probably the best sound of all slides comes from a thick bottleneck - like the one in the pic - worn on the ring finger. With mild getting used to you will most likely start producing excellent tone on any guitar or sting setup.
However, a ring finger handicap is not that easy to overcome - unless you're Django - and because IMO a good slide player plays fewer notes with his slide than with his fingers I find it best to sacrifice some intonation and wear the slide on your pinky.
Well that's all for now folks, feel free to comment with your personal experiences and opinions.