As far as I know all dynamo lights are going to be too big of a hassle to remove when you get off the bike. They all have a cable that runs down the fork and connects to the hub. You could unplug it at the fork quickly, but you would have to unwrap the cable from your fork, and then use tools to unbolt the light. If it makes you feel better I've been commuting with a dynamo light in NYC for 5 years and nobody has stolen mine. I don't leave the bike out every day though.
I've had really good luck with shimano dynamo hubs. My current dh-3n80 has over ten thousands miles on it. It still runs great, and I have never serviced it in any way. That includes year round nyc commuting plus an 8 month trip through South America. I don't think that one is disc compatible, but some of the other shimano ones are. The DH-3D71 is disc compatible, and is excellent.
I'm using a B&M IQ fly for my light. It works quite well. If I were to buy another one I would probably get the update, which is the IQ CYO.
http://www.sheldonbrown.com/harris/l...motec-hub.html