I can also recommend the Busch&Müller Dynamo lights. They are all designed for dynamo (AC, protection against overload/varying voltage, inbuilt capacitor to stay on for a few minutes when stopped, etc.), you don't have to worry about that. And although the manual says "hub dynamo", I'm running them successfully on a bottle dynamo (6V/3W). AFAIK, all dynamos are similar enough that the electronics can handle them. Many models also have electronics that change between day/night settings (useful for tunnels!) and other things.
Regarding theft, they all look fairly inconspicuous, stylish but not particularly expensive, so I don't think they attract casual thieves (experts of course will know their value). The mount is very solid, and the bolt uses a special kind of star-shaped screw; it's not totally theftproof but you can't use standard screwdrivers, and I found even with the proper tools its a bit of fiddling, so I'm not worried about theft; other bits of the bike can be taken off more easily.
The choice of model depends on your situation. Are you mostly cycling in lit areas or do you cycle in dark unlit areas?
I had the "Lumotec Lyt T Senso Plus" first, it is very good for city cycling, with a really bright area on the road so that you can see potholes and obstacles. It's also not very expensive (40 Euro). However, I often cycle through a dark park, and while the Lyt lit up the path perfectly well, I felt I wanted one with a wider beam that also lit up the sides, it just felt more comfortable and safe to see the area around the path.
So I then bought a "Luxos B" (RRP 119 Euro), which has a much wider beam. This is very good in all respects, it almost seems like a car headlight (perhaps not quite as bright, but in terms of beam width and distance that you can see). The "Luxos U" additionally has a battery and a USB charger and is much more expensive, but I'm not convinced it's a good idea. For one thing, the battery will have limited lifetime especially when outside from winter to summer, and I generally don't think you should combine different functions (light and USB charging) in the same very expensive item. The Luxos B has a capacitor so that it stays on for a few minutes when you stop, more than enough for traffic lights and such.
The B&M Website shows the beam shape and sample images, it's worth comparing the models and think about what kind of area you're cycling in.
All the B&M models are bright enough so that you are clearly visible to cars in normal street situations (the Luxos even has additional non-directional LEDs), although if you are in an arms-race situation (where everybody else has multiple superbright lights) you may feel too dark.
A bit off-topic perhaps, but as somebody mentioned it in a comment, please stay away from superbright LED lights without shaped beams, not only cheap ones but also some of the expensive brands. It is important to have a shaped beam that illuminates the path but not dazzle oncoming cars, other cyclists or pedestrians, and that they are adjusted carefully. Also please stay away from helmet-mounted lights. Or at least use them only where absolutely needed (e.g. to be seen in an already very bright environment).
My regular experience, when I cycle along through the park and somebody with a floodlight comes round the corner and completely blinds me - don't know how many times I ended up in the grass, and once I almost collided with one of the "floodlighters". The worst experience was when I suddenly faced a team of several riders, each with a superbright handle bar light and a helmet light, all looking straight at me. I couldn't see anything for minutes afterwards. Unfortunately I only managed to stammer a "too bright" before they had gone (they didn't stop to ask if I'm ok...).
So please, when you check out different lights, not only consider your own requirements, but also those of fellow path users.
