Well I will be more specific.
In Holland many bikes have locks that are more expensive than the bike itself. Stealing bikes seems to be normal here. If a bike can be removed, it will be removed, even if it is locked. In Amsterdam for instance, many people use motorcycle locks for their bicycle. It's that bad.
I'm looking for a lock & chain combination not heavier than say 3 kilograms. Maximum price about 150 euro.
Without consulting you, I would go for a listed ART 4 points lock.
http://www.stichtingart.nl/sloten/sloten.php
I have heard of thieves with Falle gear and so on. They also use mobile hydraulic cutters designed to free people from crashed cars.
You guys may know better what to buy, after examining this list.