I have the Perfection pegs in one of my violins, and the Wittners in two violins and a viola. I love them.
I prefer the Wittner, personally. I prefer the higher gear ratio, for one. Also, the Perfection pegs have this thing where you pull the peg out or push it in to make it easier or harder (respectively) to turn. I misunderstood at first, and thought I had to pull them out and push them in like regular pegs, which seemed to defeat the whole purpose. It was my misunderstanding, but it still left me not caring for them so much. And the smaller gear ratio means they can get pulled out of tune over time, although not by much. The Wittners are pretty much rock solid. They stay where you put them.
Most people still put a fine tuner on the E string, even with the Wittners. You can, and I use mine every once in a while, but if you've got a light touch, you don't really need it. The 8:1 ratio is enough to let you tune even the E. (The 4:1 isn't - if you go with Perfection Pegs, you'll definitely want a fine tuner on the E.)
I have the Knilling Perfection pegs (thanks Fiddlerman!). I installed them without glue, so it's reversible. I have read that people like the Finetune pegs and the Perfection (also Peghed) pegs. I love the find tuning aspect and I like have no fine tuners on my instrument.
Give the Wittner's a try. I'm planning on installing a set on my other violin soon, just so I can try both and see which one I like better. If you install and don't like the Wittners, I bet someone will take them off your hands (I would!), since it's reversible.
I just wanted to add that I have no fine E tuner, with the perfection pegs. Even with a 4:1 ratio I can nail the E every time. With Wittner's it would be even easier.
The only minor issue is that the gears in the Wittner are in the button; they are in the shaft for the Perfection pegs. The Wittners are plastic and a little chunkier, but it's not a huge issue. Like I said, I tried one, I'll try the other, and then I'll stick with whichever I like best.
Geared pegs weigh about as much as wooden pegs, tune better, are more stable, and you get get all the hardware off of your tailpiece, what's not to like?