It's also good practice to choose a suitable area when locking a bike up - a side alley off a street is generally quiet and a thief could be unseen. A large bike rack area outside a railway station for example is also not great since there are multiple racks for thief to work behind. There are some youtube videos though where the owner deliberately carries a large set of chain cutters and in broad daylight just walks up to his secured bike, cuts the (cheap) wire rope, and rides off - no-one notices.
Location is priority, then buy the best system for your needs/budget - no lock system is infallible, but if a thief is delayed and risks being seen/challenged then they'll find another bike to steal.