Q:
I'm getting ready to amplify my violin for the first time. What pickup do you recommend?
A:
I have a variety of pickups: Eric Aceto, LR Baggs, StringAmp, and Zeta.
I like them all for different reasons.
Here are my thoughts, purely subjective, and based on personal experience of my own sound, and the sounds of other players. I do not endorse, nor have I ever been invited to endorse any of these products...
For the most bang for your buck, I recommend the Baggs (buy the preamp as well- I use it with all of the above pickups). This is a simple solution and a very popular pickup. It is installed in the bridge, as is the Aceto, which is more expensive and sounds slightly better.
I also like the sound of the Realist and the Schertler although I haven't used them. They produce a relatively warm and natural sound. I think they may both sound a little better than the Baggs.
The least invasive installations (you can remove them without moving or changing the bridge) are the Schertler & the Fishman. Also, I'm told that Barcus Berry has a pickup out that goes on and off the instrument with ease, but I've not heard or seen it. I'd stay away from the Fishman. in my experience, it produces a rather weak, tinny and scratchy sound.
The Zeta is generally used on solid body instruments, and produces a very specific electric violin sound- not ideal if you're just trying to produce a louder acoustic violin sound.
For the loudest, cleanest, amplified violin sound (and by that I mean very loud acoustic violin, as opposed to the 'electric violin' sound I mentioned before), I like the StringAmp system. That's what I'm using with the Mahavishnu Project, and I like it a lot, despite a bit of a hum problem. It's the most invasive and complicated installation, though- you'd probably want to just buy a violin with the system already installed, as I did. It's also the most expensive pickup system I know about.
Obviously, it would be best to check out all of these options out via live performance or recordings, but since that could be difficult or impossible, I hope these observations are helpful.